Neuropathic pain in osteoarthritis: a review of pathophysiological mechanisms and implications for treatment

Reversing Microglial Polarisation by High Intensity Interval Training: A Novel Approach to Mitigate Inflammatory Responses in Osteoarthritis via Jak2/Stat3 Pathway

Osteoarthritis (OA) is associated with inflammatory responses linked to microglial polarisation within the central nervous system. However, exploring therapeutic approaches and their underlying mechanisms remains a direction for future research. The present study investigates the potential of high-intensity interval training (HIIT) to alleviate inflammation and facilitate the shift from M1 to M2 microglial polarisation via the Jak2/Stat3 pathway in an OA rat model. Wistar rats were induced with OA via intra-articular injection of monosodium iodoacetate and subsequently underwent HIIT for six consecutive weeks after a 4-week establishment period. Pain thresholds were measured using the von Frey test. Immunofluorescence detected Tmem119, SP, Glu, c-Fos, and IL-6, while flow cytometry analysed CD68 and CD163 levels. Proteomics compared the protein differences between the OA and HIIT groups. The Jak2/Stat3 pathway was activated in OA rats with C-A1 injections, followed by HIIT and subsequent Western blot analysis of inflammatory cytokines. The results indicated a significant decrease in pain threshold from the third to the tenth week in OA rats, while HIIT was found to increase pain thresholds. HIIT was found to promote M1 to M2 microglial polarisation and downregulate the expression of Tmem119, SP, Glu, c-Fos, and IL-6. Additionally, HIIT was more effective in suppressing Jak2 and Stat3 expression levels compared to OA rats. Activation of the Jak2/Stat3 pathway significantly increased the expression of Glu, c-fos, SP, and IL-6, but HIIT reversed these OA-induced increases. Compared to the OA + C-A1 group, the expression levels of Glu, c-fos, SP, and IL-6 were significantly reduced in the OA + C-A1 + HIIT group. In conclusion, HIIT effectively mitigates OA-induced inflammatory responses by reversing microglial polarisation through the Jak2/Stat3 pathway.

Preoperative Risk Factors for Persistent Pain After Total Hip Arthroplasty for Hip Osteoarthritis: The Influence of Neuropathic Pain, Central Sensitization, and Pain Catastrophizing

Background Approximately 10% of patients experience persistent pain after total hip arthroplasty (THA). Pain mechanisms, such as neuropathic pain, central sensitization, and pain rupture symptoms, have been reported to be associated with persistent postoperative pain. However, no studies have examined these mechanisms simultaneously. Therefore, in this study, we aimed to investigate the preoperative prevalence of neuropathic pain, central sensitization, and pain catastrophizing among patients with hip osteoarthritis (OA) and identify risk factors for persistent pain after THA, focusing on neuropathic pain, central sensitization, and pain catastrophizing. Methods In this retrospective study, 311 patients who underwent THA for hip OA were included. Preoperative neuropathic pain, central sensitization, and pain catastrophizing were evaluated using the pain-DETECT, Central Sensitization Inventory, and Pain Catastrophizing Scale, respectively. Persistent postoperative pain was defined as a Numerical Rating Scale score ≥3 at 12 months postoperatively. Persistent and non-persistent pain groups were compared using univariate and multivariate analyses. Results Preoperatively, neuropathic pain, central sensitization, and pain catastrophizing were present in 84 (27.0%), 74 (23.8%), and 183 (58.8%) of patients, respectively. In this study, 36 (11.6%) patients experienced persistent pain. The persistent pain group had a significantly higher prevalence of central sensitization and pain catastrophizing than the non-persistent pain group (P < 0.01). Multivariate analysis revealed central sensitization and pain catastrophizing as independent risk factors for persistent postoperative pain. Conclusion This study highlights the importance of preoperative assessment of central sensitization and pain catastrophizing in predicting persistent pain after THA for hip OA. Addressing these factors using targeted interventions may improve postoperative outcomes and patient satisfaction.

Brain functional imaging contributions in osteoarthritis-related pain: A viewpoint

Objective

Neuroimaging investigations are critical to provide a more direct assessment of brain disturbances associated with osteoarthritis (OA)-related pain, and to better understand its pathophysiology to develop new treatment strategies. This viewpoint aims to summarize the importance of the brain in OA pain.

Method

A European working group on pain in osteoarthritis GO-PAIN (Going Inside Osteoarthritis-related Pain Phenotyping) has been created to work on a global assessment of the OA-related pain. Relevant scientific literature was evaluated, summarized and discussed to expose advances in functional brain alterations related-to OA pain.

Results

Findings of neuroimaging studies are highly heterogenous and based on small sample size, but some key brain alterations associated with OA pain can be identified across experiments. A systematic literature review conducted by Hall and colleagues (2023) found lower activity, connectivity, and grey matter volume in the right anterior insula in patients with OA than in healthy controls. Other works also pointed out that activity of specific brain regions could serve as a potential surrogate biomarker, but several limitations and confounding factors needs to be addressed.

Conclusions

Brain functional imaging provides opportunities to accurately address an OA-related pain endophenotype. To encompass limitations and fill the gaps from the previous studies, we propose a blueprint for the next 5 years and stimulate ideas for others working in the field.

Patterns of analgesic utilisation among people with knee osteoarthritis: a cohort study using UK primary care data

Background

Osteoarthritis (OA) is a prevalent disabling joint disease affecting more than 300 million people globally and knees are most commonly affected. It is associated with pain and functional limitation that adversely affect mental well-being and compromise quality of life. Analgesic use is common among patients with knee osteoarthritis (KOA), however, data on patterns of analgesics use at an individual patient level are sparse. The present study describes patterns of analgesic use, by determining the proportion of persistent users within one year of therapy initiation in patients with KOA.

Methods

A retrospective cohort study using the clinical practice research datalink. Analgesic prescriptions for adults with an incident KOA diagnosis were captured and grouped into five exposure groups including: antidepressants, antiepileptic drugs (AEDs), opioids, non-steroidal anti-inflammatory drugs (NSAIDs) and paracetamol. A persistent user was a person who used >180 defined daily doses (DDDs) per year and had prescriptions in at least three out of the four quarters of the year.

Results

Variable proportions of patients used respective analgesic classes persistently during the first year after prescribing; 36.8% of antidepressant users, 27.0% of NSAIDs, 23.8% of AEDs, 17.5% of paracetamol and 14.9% of opioid users were persistent users. Across classes, persistent users were slightly younger, were issued more prescriptions and used higher doses of analgesics compared to non-persistent users.

Conclusion

Between 14.9% and 36.8% became persistent analgesic users by the end of the first year after their initial prescription. The study applied meaningful clinical attributes to define persistence. This informs future research on clinical and adverse drug outcomes in persistent users compared to non-persistent users across five separate analgesic classes.

Pain Management in the Older Adults: A Narrative Review

With the increase in life expectancy in the United States, octogenarians and nonagenarians are more frequently seen in clinical practice. The older adults patients have multiple preexisting comorbidities and are on multiple medications, which can make pain management complex. Moreover, the older adults population often suffers from chronic pain related to degenerative processes, making medical management challenging. In this review, the authors collated available evidence for best practices for pain management in the older adults.

The validation and cross-cultural adaptation of the PainDETECT questionnaire in osteoarthritis-related pain

BACKGROUND

Patients with knee osteoarthritis (KOA) often experience persistent pain and functional impairment after total knee arthroplasty (TKA), which presents challenges for pain management. Accurate preoperative assessment of pain characteristics is crucial for tailoring individualized treatment plans. The PainDETECT Questionnaire has been widely used to identify neuropathic components in chronic pain and has been validated for its reliability and validity across various cultural contexts. However, a culturally adapted version tailored to Chinese patients is currently lacking. This study aims to translate and culturally adapt PainDETECT for Chinese patients and evaluate its validity in TKA patients in China.

METHODS

This study followed international guidelines to translate and adapt the PainDETECT Questionnaire (PDQ) into Chinese (PDQ-CV). A cohort of 241 knee osteoarthritis (KOA) patients completed the PDQ-CV, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), EuroQol-5 Dimensions-5 Levels (EQ-5D-5 L), and Central Sensitization Inventory Chinese Version (CSI-CV). We assessed internal consistency using Cronbach's alpha and test-retest reliability via intraclass correlation coefficient (ICC). Construct and structural validity were evaluated through Pearson correlations and factor analyses.

RESULTS

The PDQ-CV demonstrated good acceptability among KOA patients, with no floor or ceiling effects observed. Internal consistency was high (Cronbach's α = 0.896), and test-retest reliability was excellent (ICC = 0.994; 95% CI: 0.943-1.045). The PDQ-CV total score showed significant positive correlations with WOMAC (r = 0.589, P < 0.01), EQ-5D-5 L (r = 0.533, P < 0.01), and CSI-CV (r = 0.776, P < 0.01). Exploratory factor analysis (EFA) extracted two primary factors, corresponding to the sensory dimension (52.1% variance) and the affective dimension (16.3% variance), explaining a total variance of 68.4%.

CONCLUSION

The PDQ-CV demonstrated good feasibility, reliability, and validity in Chinese KOA patients, supporting its use in clinical practice and providing a foundation for future research.

A multi-modal evaluation of experimental pain and psychological function in women with carpometacarpal osteoarthritis

Objective

Thumb carpometacarpal osteoarthritis (CMC1 OA) is a prevalent and debilitating condition that lacks effective treatments. Understanding the multidimensional pain experience across CMC1 OA disease stages is crucial to improving treatment outcomes. This study examined how radiographic CMC1 OA severity is associated with physical, psychological, and somatosensory function.

Method

Thirty-one women with early-stage (Eaton-Littler 1-2) or end-stage (Eaton-Littler 3-4) radiographic CMC1 OA completed validated questionnaires to assess pain, disability, and psychological function. Additionally, experimental pain was measured in each participant using quantitative sensory testing (QST) (mechanical, pressure, vibratory, thermal) at seven body sites (thenar, hypothenar, brachioradialis bi-laterally; quadriceps on affected side). Cohort differences (early-vs. end-stage) across all variables were analyzed using a multivariable modeling approach that included fixed effects and interactions; notably, age was controlled as a confounder.

Results

End-stage CMC1 OA participants had higher scores in the pain (p ​= ​0.01) and function (p ​= ​0.02) portions of the AUSCAN assessment, self-reported disability of the DASH questionnaire (p ​= ​0.04), and painDETECT scores (p ​= ​0.03), indicating greater pain and disability compared to early-stage participants. Additionally, end-stage CMC1 OA participants demonstrated reduced vibratory detection and heat pain thresholds at multiple body sites (p's ​< ​0.05), with significant interactions observed across the mechanical and cold stimuli.

Conclusion

Findings revealed women with end-stage CMC1 OA exhibited increased neuropathic pain characteristics and somatosensory loss compared to those with early-stage CMC1 OA. These results underscore the importance of addressing both peripheral and centralized pain mechanisms and the need for multimodal approaches in the treatment of CMC1 OA.

Alpha-ketoglutarate ameliorates age-related and surgery induced temporomandibular joint osteoarthritis via regulating IKK/NF-κB signaling

Recent studies have shed light on the important role of aging in the pathogenesis of joint degenerative diseases and the anti-aging effect of alpha-ketoglutarate (αKG). However, whether αKG has any effect on temporomandibular joint osteoarthritis (TMJOA) is unknown. Here, we demonstrate that αKG administration improves condylar cartilage health of middle-aged/aged mice, and ameliorates pathological changes in a rat model of partial discectomy (PDE) induced TMJOA. In vitro, αKG reverses IL-1β-induced/H2O2-induced decrease of chondrogenic markers (Col2, Acan and Sox9), and inhibited IL-1β-induced/ H2O2-induced elevation of cartilage catabolic markers (ADAMTS5 and MMP13) in condylar chondrocytes. In addition, αKG downregulates senescence-associated (SA) hallmarks of aged chondrocytes, including the mRNA/protein level of SA genes (p16 and p53), markers of nuclear disorders (Lamin A/C) and SA-β-gal activities. Mechanically, αKG decreases the expressions of p-IKK and p-NF-κB, protecting TMJ from inflammation and senescence-related damage by regulating the NF-κB signaling. Collectively, our findings illuminate that αKG can ameliorate age-related TMJOA and PDE-induced TMJOA, maintain the homeostasis of cartilage matrix, and exert anti-aging effects in chondrocytes, with a promising therapeutic potential in TMJOA, especially age-related TMJOA.

Impact of Chondrocyte Inflammation on Glial Cell Activation: The Mediating Role of Nitric Oxide

OBJECTIVE

This study investigates how the inflammatory response of ATDC5 murine chondrogenic cells influences the activity of C6 (rat) and GL261 (mouse) glial cell lines. Prior research suggested nitric oxide (NO) involvement in cartilage-immune crosstalk. The current study explores whether NO, produced by inflamed chondrocytes, mediates signaling between chondrocytes and glial cells.

DESIGN

Pre-challenged ATDC5 cells with 250 ng/ml of lipopolysaccharide (LPS) were cocultured with GL261 or C6 glioma cells for 24 h with a transwell culture system. Cell viability was assessed using MTT assay. Gene and protein expression were evaluated by qRT-PCR and WB, respectively.

RESULTS

Real-time reverse transcription-polymerase chain reaction (RT-qPCR) indicated statistically significant upregulation of LCN2, IL-6, TNF-α, IL-1β, and GFAP in glial cells following 24-h coculture with challenged ATDC5 cells. Suppression of LPS-induced NO production by aminoguanidine decreased LPS-mediated LCN2 and IL-6 expression in glioma cells. We identified also the involvement of the ERK1/2 and AKT signaling pathways in the glial neuroinflammatory response.

CONCLUSIONS

This study demonstrates, for the first time, that NO produced by inflamed murine chondrocytes mediated pro-inflammatory responses in glial cells via ERK1/2 and AKT signaling, highlighting a potential mechanism linking cartilage NO to neuroinflammation and chronic pain in osteoarthritis.

Battling pain from osteoarthritis: causing novel cell death

Osteoarthritis (OA) is a significant contributor to pain and disability worldwide. Pain is the main complaint of OA patients attending the clinic and has a large impact on their quality of life and economic standards. However, existing treatments for OA-related pain have not been shown to achieve good relief. The main focus is on preventing and slowing the progression of OA so that the problem of OA pain can be resolved. Pain caused by OA is complex, with the nature, location, duration, and intensity of pain changing as the disease progresses. Previous research has highlighted the role of various forms of cell death, such as apoptosis and necrosis, in the progression of pain in OA. Emerging studies have identified additional forms of novel cell death, such as pyroptosis, ferroptosis, and necroptosis that are linked to pain in OA. Different types of cell death contribute to tissue damage in OA by impacting inflammatory responses, reactive oxygen species (ROS) production, and calcium ion levels, ultimately leading to the development of pain. Evidence suggests that targeting novel types of cell death could help alleviate pain in OA patients. This review delves into the complex mechanisms of OA pain, explores the relationship between different modes of novel cell death and pain, and proposes novel cell death as a viable strategy for the treatment of these conditions, with the goal of providing scientific references for the development of future OA pain treatments and drugs.

Neuropathic pain is a feature in patients with symptomatic femoral acetabular impingement

Femoral acetabular impingement syndrome (FAIS) is a cause of hip pain thought to be nociceptive, although pain phenotypes e.g., burning, pain attacks, prickling, numbness etc., are reported, mimicking neuropathic pain. Although no lesion to the somatosensory system is identified, neuropathic pain (NeP) may explain why nociceptive-focussed treatments are not always successful.

OBJECTIVE

To identify NeP in patients with FAIS and investigate if related to poorer outcomes.

DESIGN

A secondary analysis of the Femoral Acetabular Impingement Trial (FAIT). Outcome of interest: PainDETECT questionnaire; secondary outcomes of interest; International Hip Outcome Tool (iHOT33), Hospital Anxiety and Depression Scale (HADS) and VAS 'average pain over a month', at baseline and 8 months follow-up. Intervention (surgery or physiotherapy) were pooled.

RESULTS

173 data sets at baseline; 123 at 8 months follow-up. Baseline painDETECT identified three groups: 69% nociceptive, 19% unclear and 12% neuropathic pain phenotypes. Baseline, median scores were higher for the neuropathic group compared to the nociceptive group demonstrating borderline anxiety (9.5(5.3 to 14.2), 5(3 to 8), higher normal values for depression (7.5(2.3 to 11.8), (4(2 to 9), higher average pain (7 (6 to 8), 5(4 to 6) and lower iHOT33 14.2(9 to 21.1), 38.4(26.2 to 55.7). Post treatment, there was a median change in the neuropathic score in both iHOT33 (40.8 (25 to 76.5) with a median difference of 24.13 (CI 95% 10.46 to 45.92) and average pain 4.5(1.5 to 7) with a median difference of 2 (CI 95% 1 to 5) but to a lesser amount than the nociceptive group, iHOT33 (64(38.2 to 86.6) with a median difference of 15.50 (CI 95% 6.41 to 21.82) and average pain 3(1 to 5.7) with a median difference of 1 (CI 95% 0.5 to 1).

CONCLUSION

NeP exists in symptomatic FAIS patients and is associated with increased average pain, and functional limitations. Nociceptive-targeted treatment improves hip function and pain but with less improvement in the NeP group when compared to the nociceptive group. Pain phenotyping before intervention may improve outcomes. CONTRIBUTION OF PAPER.

The association between anxiety and depression symptoms and clinical and pain characteristics in patients with hip and knee osteoarthritis

OBJECTIVES

This study aimed to estimate the prevalence of anxiety and depression symptoms and explore the association between these symptoms and clinical and pain characteristics in patients with chronic pain (CP) due to hip and knee osteoarthritis (OA).

METHODS

In this cross-sectional study, adult patients with CP and knee and/or hip OA were included. Anxiety and depression symptoms were assessed using the Hospital Anxiety and Depression Scale. Visual analogue scale, Western Ontario and McMaster Universities Arthritis Index (WOMAC) and PainDetect Questionnaire assessed pain characteristics and Health Assessment Questionnaire (HAQ) evaluated functional disability. Correlation coefficients were used to explore the associations between anxiety and depression symptoms and clinical and pain characteristics.

RESULTS

A total of 61 patients (age 66.2±9.4 years, 67.2% female) were included. Most patients (70.5%) had clinically significant anxiety and/or depression symptoms. Patients with anxiety and/or depression symptoms had higher pain severity (p=0.032) and disability (p=0.014). Depression symptoms had a moderate positive correlation with WOMAC physical function subscale (r=0.520), WOMAC total (r=0.511) and HAQ (r=0.405).

CONCLUSIONS

Anxiety and depression symptoms are prevalent in knee or hip OA patients with CP and were associated with higher pain severity and functional disability. These findings support the screening of anxiety and depression symptoms in OA patients, in order to develop more effective multidisciplinary treatments.

Cannabinoid CB2 receptor orthologues; in vitro function and perspectives for preclinical to clinical translation

Cannabinoid CB2 receptor agonists are in development as therapeutic agents, including for immune modulation and pain relief. Despite promising results in rodent preclinical studies, efficacy in human clinical trials has been marginal to date. Fundamental differences in ligand engagement and signalling responses between the human CB2 receptor and preclinical model species orthologues may contribute to mismatches in functional outcomes. This is a tangible possibility for the CB2 receptor in that there is a relatively large degree of primary amino acid sequence divergence between human and rodent. Here, we summarise CB2 receptor gene and protein structure, assess comparative molecular pharmacology between CB2 receptor orthologues, and review the current status of preclinical to clinical translation for drugs targeted at the CB2 receptor, focusing on comparisons between human, mouse and rat receptors. We hope that raising wider awareness of, and proposing strategies to address, this additional challenge in drug development will assist in ongoing efforts toward successful therapeutic translation of drugs targeted at the CB2 receptor. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Clinical Assessment of Osteoarthritis Pain: Contemporary Scenario, Challenges, and Future Perspectives

The multifaceted nature of osteoarthritis (OA) pain presents a challenge in understanding and managing the condition. The diverse pain experiences, progression rates, individual responses to treatments, and complex disease mechanisms contribute to heterogeneity in the clinical studies outcomes. The lack of a standardized methodology for assessing and classifying OA pain challenges healthcare practitioners. This complicates the establishment of universally applicable protocols or standardized guidelines for treatment. This article explores the heterogeneity observed in clinical studies evaluating OA pain treatments, highlighting the necessity for refined methodologies, personalized patient categorization, and consistent outcome measures. It discusses the role of the multidimensional nature of OA pain, underlying pain mechanisms, and other contributing factors to the heterogeneity in outcome measures. Addressing these variations is crucial to establishing a more consistent framework for evidence-based treatments and advancing care of the patient with OA pain.

Assessment of Neuropathic Pain in Erosive Hand Osteoarthritis

Background/Objectives: Erosive hand osteoarthritis (EHOA) is an aggressive form of hand osteoarthritis (OA) and a severely disabling condition. Patients affected by OA frequently lament symptoms suggestive of neuropathic pain (NP). The aim of our study was to ascertain the presence and severity of NP in patients with EHOA and correlate its presence with EHOA clinical characteristics. Methods: In this retrospective study, we included all consecutive EHOA patients with NP symptoms who underwent upper limb electroneurography (ENoG) and nerve ultrasound. The presence of NP was screened using the ID pain neuropathic pain-screening questionnaire (ID-Pain). In addition, the following NP questionnaires were also used: Douleur Neuropathique en 4 Questions (DN4), PainDETECT, and Neuropathic Pain Symptom Inventory (NPSI). Moreover, patients completed the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) and Dreiser's algofunctional finger index questionnaires assessing EHOA disease activity. The following clinical and laboratory data were collected: age, sex, BMI, disease duration, intensity of pain (VAS 0-10), painful and swollen joints, and inflammatory indices, as well as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Results: Of the 34 patients studied, 24 (70.6%) presented NP to the ID-Pain questionnaire. According to DN4, 14 (41.2%) patients had NP, while using the PainDETECT questionnaire, 67.6% had NP. Patients with NP were statistically younger and had a higher VAS pain score compared to subjects without NP. The ENoG and median nerve ultrasound were normal in 81% of patients, while four patients had carpal tunnel syndrome. The ID-Pain questionnaire correlated with the number of painful joints (r = 0.48, p = 0.03) and with the AUSCAN questionnaire (r = 0.37, p = 0.05). The DN4 questionnaire correlated with PainDETECT (r = 0.58, p < 0.01). The PainDETECT questionnaire correlated with VAS pain (r = 0.49, p = 0.02), the DN4 questionnaire (r = 0.58, p < 0.01), and AUSCAN (r = 0.51, p = 0.02). The NPSI questionnaire correlated negatively with BMI (r = -0.53, p = 0.01) and positively with the PainDETECT questionnaire (r = 0.49, p = 0.02). Conclusions: Our study revealed that 32% to 70% of EHOA patients exhibited symptoms consistent with NP, with observed variability depending on the questionnaire utilized. Despite patients frequently exhibiting symptoms compatible with NP, only 19% of patients presented alterations on ENoG and ultrasound examinations confirming CTS. This suggests a probable nociplastic component for pain in patients with EHOA, which warrants tailored treatment. In the present study, NP correlated with clinical and functional indices of EHOA.

Neuropathic pain in patients with osteoarthritis of the hip before and after total hip arthroplasty

OBJECTIVES

The pain associated with osteoarthritis (OA) was thought to be nociceptive; however, neuropathic pain is also observed. We investigated the relationship between hip OA and neuropathic pain using the PainDETECT questionnaire (PDQ).

METHODS

A total of 159 hips of 146 consecutive patients who underwent total hip arthroplasty (THA) with a diagnosis of OA were enrolled in this study. The prevalence of each pain phenotype was evaluated preoperatively and at 6 months postoperatively using the PDQ. Patient characteristics and numerical rating scale (NRS) scores were compared between a group with possible neuropathic pain (NP group) and a group with nociceptive pain (non-NP group).

RESULTS

Before THA, neuropathic, unclear, and nociceptive pain was observed in 18, 36, and 105 hips, respectively. The prevalence in the NP group was 54 hips, accounting for approximately one-third of all hips, which decreased significantly to seven hips after THA. A significantly higher NRS score was observed in the NP group, both before and after THA.

CONCLUSION

Approximately one-third of the patients with hip OA had neuropathic pain. Therefore, neuropathic pain should be considered when treating patients with hip OA.

Exploration beyond osteoarthritis: the association and mechanism of its related comorbidities

Osteoarthritis is the most prevalent age-related degenerative joint disease and a leading cause of pain and disability in aged people. Its etiology is multifaceted, involving factors such as biomechanics, pro-inflammatory mediators, genetics, and metabolism. Beyond its evident impact on joint functionality and the erosion of patients' quality of life, OA exhibits symbiotic relationships with various systemic diseases, giving rise to various complications. This review reveals OA's extensive impact, encompassing osteoporosis, sarcopenia, cardiovascular diseases, diabetes mellitus, neurological disorders, mental health, and even cancer. Shared inflammatory processes, genetic factors, and lifestyle elements link OA to these systemic conditions. Consequently, recognizing these connections and addressing them offers opportunities to enhance patient care and reduce the burden of associated diseases, emphasizing the need for a holistic approach to managing OA and its complications.

Etiological factors of chronic pain syndrome in young adults with post-coronavirus disease 2019 condition

PURPOSE

The coronavirus disease 2019 (COVID-19) generates long-term sequelae, but studies investigating patients with chronic pain syndrome (CPS) are limited. This study aimed to establish the etiological factors of CPS in patients with post-COVID-19 conditions.

METHODS

This was a case-control retrospective study. The predictor variables were sex, diabetes mellitus, obesity (predisposing factors), unfavorable socioeconomic conditions, impaired rehabilitation (disabling factors), repeated exposure to COVID-19 (precipitating factor), home isolation, stress overload, fear of dying, admission to intensive care unit, prone positioning, and use of medications (reinforcing factors). The outcome variable was the presence of CPS.

FINDINGS

This study included 120 individuals. Prolonged days of isolation (p = 0.005), fear (p < 0.001), stress overload (p < 0.001), and impaired rehabilitation (p = 0.003) were significantly associated with CPS.

CONCLUSIONS

A significant relationship was found between prolonged days of isolation, fear, stress overload, impaired rehabilitation, and CPS.

IMPLICATIONS FOR NURSING PRACTICE

The study findings can assist nurses by promoting their knowledge of the causes of CPS and supporting the care planning needs of patients with post-COVID-19 conditions, in addition to promoting the use of the NANDA-International taxonomy.

Description of Novel Molecular Factors in Lumbar DRGs and Spinal Cord Factors Underlying Development of Neuropathic Pain Component in the Animal Model of Osteoarthritis

Osteoarthritis (OA) is one of the most common joint disorder, with pain accompanied by functional impairment, as the most pronounced clinical symptom. Currently used pharmacotherapy involves symptomatic treatment that do not always provide adequate pain relief. This may be due to concomitance of central sensitization and development of neuropathic features in OA patients. Here we performed studies in the animal model of OA to investigate of the neuropathic component. Intraarticular injection of monoiodoacetate (MIA, 1 mg) was used to induce OA in Wistar male rats. Development of pain phenotype was assessed by behavioral testing (PAM test and von Frey's test), while corresponding changes in dorsal root ganglia (DRGs L3-L5) and spinal cord (SC) gene expression were assessed by means of qRT-PCR technique. We also performed microtomography of OA-affected knee joints to correlate the level of bone degradation with observed behavioral and molecular changes. We observed gradually developing remote allodynia after MIA treatment, indicating the presence of neuropathic component. Our results showed that, among DRGs innervating knee joint, development of central sensitization is most likely due to peripheral input of stimuli through DRG L5. In SC, development of secondary hypersensitivity correlated with increased expression of TAC1 and NPY. Our studies provided molecular records on abnormal activation of pain transmission markers in DRG and SC during development of OA that are responsible for the manifestation of neuropathic features. The obtained results increase insight into molecular changes occurring in the neuronal tissue during OA development and may contribute to readdressing treatment paradigms.

Neuropathic-like pain in knee osteoarthritis: exploring differences in knee loading and inflammation. A cross-sectional study

BACKGROUND

A subgroup of patients with knee osteoarthritis (OA) reports symptoms attributable to a neuropathic cause. Little to no attention has been invested on investigating differences in knee loading and inflammation in these patients.

AIM

To explore differences in inflammation and knee loading in patients with knee OA categorized based on the presence of neuropathic-like pain.

DESIGN

Cross-sectional study.

SETTING

Ghent University Hospital, Ghent, Belgium.

POPULATION

Knee OA patients.

METHODS

cross-sectional analysis of data from 96 patients (mean age 64.18±7.11 years) with primary knee OA participating in a randomized controlled trial. Participants were divided into three groups (unlikely, possible and indication of neuropathic-like pain) according to the modified painDETECT questionnaire (mPDQ). Data on demographics, symptoms and physical function were obtained by questionnaires. Effusion/synovitis and bone marrow lesions (BMLs) were measured using magnetic resonance imaging. Knee loading variables (knee adduction moment [KAM], KAM impulse, and knee flexion moment [KFM]) were assessed by 3D-motion analysis. One-way analysis of covariance (ANCOVA), Chi-square test and curve analyses were used to analyze continuous, categorical and loading variables respectively. Multinomial logistic regression was used to identify predictors for neuropathic-like pain.

RESULTS

Patients with indication of neuropathic-like pain exhibited higher KAM impulse compared to those with no indication of neuropathic-like pain (standard mean difference (SMD): -0.036 Nm normalized to body weight and height per second, 95% CI: -0.071, -0.001) along with greater pain intensity (SMD: 3.87 units, 95% CI: 1.90, 5.84), stiffness (SMD: 1.34 units, 95% CI: 0.19, 2.48) and worse physical function (SMD: 13.98 units 95% CI: 7.52, 20.44). Curve analysis showed no significant differences in KFM and KAM between groups. Effusion/synovitis and BMLs did not differ significantly between groups. The best predictors for indication of neuropathic-like pain were KAM impulse, Hoffa and sex.

CONCLUSIONS

Knee OA patients with indication of neuropathic-like pain exhibited higher dynamic medial loading, greater pain severity and worse physical function, while inflammatory markers were not significantly different across mPDQ groups. Future longitudinal studies are warranted to strengthen the evidence and establish mechanisms to explain associations between neuropathic-like pain and knee loading.

CLINICAL REHABILITATION IMPACT

Knee loading is a modifiable factor and patients with neuropathic-like pain may benefit from offloading interventions.

Central Sensitization and Neuropathic Pain Cumulatively Affect Patients Reporting Inferior Outcomes Following Total Knee Arthroplasty

UPDATE

This article was updated on November 17, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 102, the text that had read "In a post hoc analysis of the preoperative results, Group 1 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). Groups 2 and 3 showed worse preoperative WOMAC pain, function, and total subscores compared with Group 4 (p < 0.05 for all). These results remained the same at 2 years after surgery." now reads "In a post hoc analysis of the preoperative results, Groups 1, 2, and 3 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). At 2 years postoperatively, Group 1 showed inferior WOMAC pain, function, and total scores compared with the other groups (p < 0.05 for all). Also, Groups 2 and 3 had worse WOMAC pain, function and total scores compared with Group 4 (p < 0.05 for all)." Also, on page 106, the title of Table IV, which had previously read "Inter-Group Comparison of Preoperative Scores (Post Hoc Analysis)" now reads "Inter-Group Comparison of Postoperative Scores (Post Hoc Analysis)."

Neuropathic pain in patients with primary knee osteoarthritis: A cross-sectional study

INTRODUCTION

Neuropathic pain (NP) is believed to be a distinct subtype of pain associated with knee osteoarthritis (KO). This study aimed to determine the prevalence of NP in patients with primary KO and examine its correlation with various factors.

METHODS

A cross-sectional study was conducted on 195 patients with primary KO who did not have the following conditions: knee surgery, infection, rheumatic diseases, peripheral and central neurological diseases, patients who received treatment for neuropathic pain in the past 6 months, diabetes, renal failure, and alcoholism. NP was evaluated using two standardized questionnaires, the Douleur Neuropathique 4 questions (DN4) and the painDETECT questionnaire.

RESULTS

The majority of patients were female (87.5%), with a mean age of 59.15 ± 7.62 years. NP was detected in 55.9% of patients according to the DN4 questionnaire and in 50.7% of patients according to the painDETECT questionnaire. The DN4 score was positively correlated with age (p=0.041; rs=0.145), visual analogue scale (VAS)-pain at rest (p=0.009; rs=0.188), VAS-pain at movement (p=0.017; rs=0.173), Western Ontario and McMaster Osteoarthritis Index (WOMAC) pain score (p=0.030; rs=0.157), WOMAC stiffness score (p=0.000; rs=0.253), physical function WOMAC score (p=0.000; rs=0.271), total WOMAC score (p=0.000; rs=0.305), Lequesne score (p=0.002; rs=0.221), and negatively correlated with quadriceps circumference (p=0.008; rs=-0.210). Whereas, the painDETECT score was positively correlated with VAS-pain at movement (p=0.002; rs=0.220), WOMAC stiffness score (p=0.043; rs=0.147), physical function WOMAC score (p=0.017; rs=0.172), and total WOMAC score (p=0.012; rs=0.182). NP according to the DN4 was associated with quadriceps circumference (p=0.01), while the painDETECT score was associated with VAS- pain at movement scores (p=0.022) and total WOMAC score (P=0.001).

CONCLUSION

This study found that NP is common among patients with primary KO and is associated with more painful pathology and functional impairment. These findings highlight the importance of recognizing and managing NP in this population to improve patient outcomes.

Injection of kaolin/carrageenan in the rat knee joint induces progressive experimental knee osteoarthritis

ABSTRACT

Osteoarthritis (OA), the most common joint disorder worldwide, is characterized by progressive degeneration of articular and periarticular structures, leading to physical and emotional impairments that greatly affect the quality of life of patients. Unfortunately, no therapy has been able to halt the progression of the disease. Owing to the complexity of OA, most animal models are only able to mimic a specific stage or feature of the human disorder. In this work, we demonstrate the intraarticular injection of kaolin or carrageenan leads to the progressive degeneration of the rat's knee joint, accompanied by mechanical hyperalgesia and allodynia, gait impairments (reduced contact area of the affected limb), and radiological and histopathological findings concomitant with the development of human grade 4 OA. In addition, animals also display emotional impairments 4 weeks after induction, namely, anxious and depressive-like behaviour, important and common comorbidities of human OA patients. Overall, prolonging kaolin or carrageenan-induced monoarthritis mimics several important physical and psychological features of human OA in both male and female rodents and could be further applied in long-term studies of OA-associated chronic pain.

Home-Based Remote Rehabilitation Leads to Superior Outcomes for Older Women With Knee Osteoarthritis: A Randomized Controlled Trial

OBJECTIVES

To examine the effects of a home-based lower-extremity strengthening exercise program in community-dwelling older women with knee osteoarthritis.

DESIGN

Randomized controlled trial.

SETTING AND PARTICIPANTS

Women aged ≥60 years with knee osteoarthritis and Kellgren-Lawrence grade 1 or 2 on anteroposterior/lateral radiographs of both knee joints.

METHODS

Patients (n = 36) were randomly divided into experimental (EG) and control (CG) groups. The EG performed home-based remote rehabilitation lower-extremity strengthening exercises for 8 weeks, whereas the CG received no intervention. Assessment was performed at baseline and week 8. The primary outcome was the five-times sit-to-stand test (FTSST) result. Secondary outcomes included timed up-and-go (TUG) test results, knee extensor and flexor strength, quadriceps (rectus femoris) muscle activity, skeletal muscle index, blood pressure (BP), visual analog scale (VAS) scores, C-reactive protein level, and erythrocyte sedimentation rate.

RESULTS

A statistically significant difference in the FTSST times was observed between the groups after 8 weeks of intervention (EG: 7.95 ± 1.08 seconds, CG: 10.01 ± 2.03 seconds, P < .001). In the EG, the TUG test score decreased by 0.75 ± 0.80 seconds (P = .002), right and left knee flexor strength increased by 4.69 ± 6.05 kg (P = .007) and 3.98 ± 6.98 kg (P = .038), respectively, and the right knee extensor root mean square (RMS) ratio increased by 1.24 ± 0.39 (P = .027). Additionally, systolic and diastolic BP decreased by 9.50 ± 10.75 mm Hg (P = .005) and 4.25 ± 4.91 mm Hg (P = .003), respectively. In the CG, the VAS scores decreased by 9.10 ± 13.68 mm (P = .022).

CONCLUSIONS AND IMPLICATIONS

The home-based exercise program using a remote rehabilitation medical device was effective in improving lower extremity strength and function in community-dwelling older women with knee osteoarthritis. This finding suggests that the remote rehabilitation medical device may be used as an alternative to exercise interventions for patients with knee osteoarthritis.

Neuropathic Pain Associated With First Metatarsophalangeal Joint Osteoarthritis: Frequency and Associated Factors

OBJECTIVE

To determine whether neuropathic pain is a feature of first metatarsophalangeal (MTP) joint osteoarthritis (OA).

METHODS

A total of 98 participants (mean ± SD age 57.4 ± 10.3 years) with symptomatic radiographic first MTP joint OA completed the PainDETECT questionnaire (PD-Q), which has 9 questions regarding the intensity and quality of pain. The likelihood of neuropathic pain was determined using established PD-Q cutoff points. Participants with unlikely neuropathic pain were then compared to those with possible/likely neuropathic pain in relation to age, sex, general health (Short Form 12 [SF-12] health survey), psychological well-being (Depression, Anxiety and Stress Scale), pain characteristics (self-efficacy, duration, and severity), foot health (Foot Health Status Questionnaire [FHSQ]), first MTP dorsiflexion range of motion, and radiographic severity. Effect sizes (Cohen's d coefficient) were also calculated.

RESULTS

A total of 30 (31%) participants had possible/likely neuropathic pain (19 possible [19.4%], 11 likely [11.2%]). The most common neuropathic symptoms were sensitivity to pressure (56%), sudden pain attacks/electric shocks (36%) and burning (24%). Compared to those with unlikely neuropathic pain, those with possible/likely neuropathic pain were significantly older (d = 0.59, P = 0.010), had worse SF-12 physical scores (d = 1.10, P < 0.001), pain self-efficacy scores (d = 0.98, P < 0.001), FHSQ pain scores (d = 0.98, P < 0.001), and FHSQ function scores (d = 0.82, P < 0.001), and had higher pain severity at rest (d = 1.01, P < 0.001).

CONCLUSION

A significant proportion of individuals with first MTP joint OA report symptoms suggestive of neuropathic pain, which may partly explain the suboptimal responses to commonly used treatments for this condition. Screening for neuropathic pain may be useful in the selection of targeted interventions and may improve clinical outcomes.

Pain Management in the Elderly: A Narrative Review

With the increase in life expectancy in the United States, octogenarians and nonagenarians are more frequently seen in clinical practice. The elderly patients have multiple preexisting comorbidities and are on multiple medications, which can make pain management complex. Moreover, the elderly population often suffers from chronic pain related to degenerative processes, making medical management challenging. In this review, the authors collated available evidence for best practices for pain management in the elderly.

DEAD-box helicase 54 regulates microglial inflammatory response in rats with chronic constriction injuries through NF-κB/NLRP3 signaling axis

Neuropathic pain (NP) is caused by damage to or disease of the somatosensory nervous system, but its mechanism is still not fully understood. In this study, DEAD-box helicase 54 (DDX54) was targeted, and its regulatory role was explored in a chronic constriction injury (CCI) rat model. Microglia and HMC3 cells were stimulated with LPS. The interaction between DDX54 and myeloid differentiation factor-88 adapter protein (MYD88) was verified. A CCI of sciatic nerve model in rats was established. Behavioral testing was performed before and after the CCI. The expressions of IL-1β, TNF-α, and IL-6 were upregulated, and those of DDX54, MYD88, NF-κB, and NOD-like receptor 3 (NLRP3) were upregulated in microglia and HMC3 cells after LPS induction. DDX54 knockdown in microglia and HMC3 cells inhibited IL-1β, TNF-α, and IL-6 expressions and downregulated the protein levels of MYD88, p-NF-κB p65 (p-p65), and NLRP3. DDX54 overexpression promoted the stability of MYD88 mRNA. DDX54 binds to the MYD88-3'-untranslated region (UTR). DDX54 interference in rats could alleviate the decrease of paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) induced by CCI, inhibit Iba1 expression, and reduce inflammatory factors as well as MYD88 and NF-κB expressions. DDX54 promotes the activation of NF-κB/NLRP3 signaling by regulating MYD88 mRNA stability, thereby affecting inflammatory response and NP progression in CCI rats.NEW & NOTEWORTHY The role of DDX54 protein in LPS-induced microglia and a chronic constriction injury (CCI) rat model was investigated for the first time. DDX54 interference can inhibit microglial activation and reduce the secretion of inflammatory factors. The interaction between DDX54 protein and MYD88 mRNA was explored for the first time. DDX54 promotes NF-κB/NLRP3 signaling activation by regulating MYD88 transcription in a CCI rat model.

Pain in osteoarthritis from a symptom to a disease

Pain is the most frequent symptom of osteoarthritis (OA), occurring much more commonly than stiffness or disability. Classically, OA-related pain has been considered to be a nociceptive pain condition and an alarm signal correlated to the intensity of joint degradation. However, OA-related pain is a specific disease, with a complex pathophysiology, including neuropathic peripheral and central abnormalities, together with local inflammation involving all joint structures. Clinical findings emphasize that it is not a stable and linear condition, that pain experience is poorly correlated to structural modifications, and that the quality of pain in OA is important to consider, aside from its intensity. OA-related pain is modulated by many factors, including the individual patient's psychological and genetic factors, as well as the theoretical role of meteorological influences. Recent findings have improved our knowledge about the central mechanisms of OA pain, especially in persistent cases. A specific questionnaire on OA pain is currently being developed to assess more precisely the patient's experience and target specific pain mechanisms. In conclusion, OA-related pain should be analyzed specifically aside from OA, taking into account the complexity of OA pain as a disease, distinguishing different OA pain phenotypes, to guide more precisely analgesic treatment and OA global management.

The analgesic effect and safety of duloxetine in total knee arthroplasty: A systematic review

Background: Duloxetine is a serotonin and norepinephrine reuptake inhibitor (SNRI) with clinical efficacy in chronic pain conditions. In this study, we aim to evaluate the analgesic effect and safety of duloxetine in total knee arthroplasty (TKA). Methods: A systematic search was completed on MEDLINE, PsycINFO, and Embase from inception to December 2022 to find relevant articles. We used Cochrane methodology to evaluate the bias of included studies. Investigated outcomes included postoperative pain, opioid consumption, adverse events (AEs), range of motion (ROM), emotional and physical function, patient satisfaction, patient-controlled analgesia (PCA), knee-specific outcomes, wound complications, skin temperature, inflammatory markers, length of stay, and incidence of manipulations. Results: Nine articles involving 942 participants were included in our systematic review. Out of nine papers, eight were randomized clinical trials and one was a retrospective study. The results of these studies indicated the analgesic effect of duloxetine on postoperative pain, which was measured using numeric rating scale and visual analogue scale. Deluxetine was also effective in reducing the morphine requirement and wound complications and enhancing patient satisfaction after surgery. However, the results on ROM, PCA, and knee-specific outcomes were contraventional. Deluxetine was generally safe without serious AEs. The most common AEs included headache, nausea, vomiting, dry mouth, and constipation. Conclusion: Duloxetine may be an effective treatment option for postoperative pain following TKA, but further rigorously designed and well-controlled randomized trials are required.

High intensity interval training attenuates osteoarthritis-associated hyperalgesia in rats

High-intensity interval training (HIIT) is a physical therapy that may benefit patients with osteoarthritis (OA). Cacna2d1 is a calcium channel subunit protein that plays an important role in the activity of nerve cells. However, there is currently no evidence on HIIT relieving OA-associate hyperalgesia by decreased Cacna2d1. Our study established the OA rat models with intra-articular injection of monosodium iodoacetate (MIA). This experiment was divided into two stages. The first stage comprised three groups: the control, OA, and OA-HIIT groups. The second stage comprised two groups, including the AAV-C and AAV-shRNA-Cacna2d1 groups. OA rats were positioned at the L5-L6 segments, and 20 µl of AAV virus was injected intrathecally. The pain threshold, cartilage analysis, Cacna2d1, and pain neurotransmitters were measured and compared. The pain threshold was significantly lower in OA rats than in control rats from the first to the tenth week. Starting from the sixth week, OA-HIIT rats exhibited significantly increased pain thresholds. The expression of Cacna2d1 increased in OA rats. Moreover, the knockdown of Cacna2d1 significantly down-regulated the expression of c-Fos, SP, and Vglut2 in the posterior horn of the spinal cord. In conclusion, HIIT attenuates OA-associated hyperalgesia, which may be related to the down-regulation of Cacna2d1.

Inflammation and subsequent nociceptor sensitization in the bone marrow are involved in an animal model of osteoarthritis pain

AIMS

This study aimed to determine whether pathological changes in the bone marrow cause Osteoarthritis (OA) pain based on magnetic resonance imaging (MRI), immunohistochemistry, and electrophysiology.

MAIN METHODS

Adjuvant-induced arthritis (AIA) was achieved by injecting 150 μL of complete Freund's adjuvant into the right knee joints of male Sprague-Dawley rats. AIA rats were compared with saline-injected rats.

KEY FINDINGS

AIA significantly induced mechanical hyperalgesia and spontaneous pain in the right hind paw 1-14 days after induction. Intratibial injection of 50 μL of 1 % lidocaine significantly suppressed AIA-induced mechanical hyperalgesia (p = 0.0001) and spontaneous pain (p = 0.0006) 3 days after induction. In T2-weighted MRI, AIA induced high-signal intensity within the proximal tibial metaphysis, and the mean T2 values in this area significantly increased on days 3 (p = 0.0043) and 14 (p = 0.0012) after induction. AIA induced intraosseous edema and significantly increased the number of intraosseous granulocytes on days 3 (p < 0.0001) and 14 (p < 0.0001) after induction. The electrophysiological study on days 3-7 after induction showed significantly increased spontaneous firing rates (p = 0.0166) and evoked responses to cutaneous stimuli (brush, p < 0.0001; pinching, p = 0.0359) in the right hind paw plantar surface and intratibial stimuli (p = 0.0002) in wide-dynamic-range neurons of the spinal dorsal horn.

SIGNIFICANCE

Intraosseous changes caused by OA induce hypersensitivity in the sensory afferents innervating bone marrow may be involved in OA pain. Novel bone marrow-targeted therapies could be beneficial for treating OA pain.

The Effectiveness of Tuina in Relieving Pain, Negative Emotions, and Disability in Knee Osteoarthritis: A Randomized Controlled Trial

OBJECTIVE

To evaluate the effectiveness of Tuina in relieving the pain, negative emotions, and disability of patients with knee osteoarthritis (KOA).

DESIGN

Single-center, parallel, randomized controlled trial.

SETTING

Shanghai Guanghua Integrated Chinese and Western Medicine Hospital, Shanghai, China.

SUBJECTS

Adult patients with KOA who were able to speak Chinese and self-report symptoms were eligible.

METHODS

A total of 104 patients were randomly allocated to receive the 6-week treatment of Tuina (Tuina group) or celecoxib (celecoxib group). Data on pain, negative emotions, and disability were collected at baseline, at week 2, 4, and 6, and follow-up (1 month after the last treatment). The primary outcomes were the pressure pain thresholds. The secondary outcomes were: (1) numerical rating scale at rest and with movement; (2) Hamilton Anxiety Scale; (3) Hamilton Depression Scale; (4) Western Ontario and McMaster Universities Osteoarthritis Index; and (5) clinical effective rate. The adverse events of the trial were evaluated.

RESULTS

In total, 99 patients completed the follow-up. Generalized linear mixed models were constructed to analyse the between-group differences. Statistically significant differences were found in the interaction effects (P < .05). In evaluating the group effect, statistical differences were found at week 6 and follow-up (P < .05). Further, all variables showed a time effect (P < .05). A statistical difference in the clinical effective rate was found between the Tuina and celecoxib groups (P < .05).

CONCLUSIONS

Tuina produced superior effects for pain, negative emotions, and disability over time, as compared to celecoxib in patients with KOA.

Genicular Nerve Block for Pain Management in Patients With Knee Osteoarthritis: A Randomized Placebo-Controlled Trial

OBJECTIVE

This study was undertaken to determine the efficacy of ultrasound-guided genicular nerve block (GNB) for the management of knee pain in patients with knee osteoarthritis.

METHODS

We performed a 12-week parallel-group, placebo-controlled randomized trial of GNB. Within 2 weeks of randomization, patients with knee osteoarthritis in the active arm received 3 injections of 5.7 mg celestone chronodose (1 ml) and 0.5% bupivacaine (3 ml) to the inferomedial, superomedial, and superolateral genicular nerves; patients with knee osteoarthritis in the placebo arm received injections of normal saline. At baseline and at weeks 2, 4, 8, and 12, patients recorded their pain and disability on a 100-mm visual analog scale (VAS) (the primary outcome measure), the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC), and the Intermittent and Constant Osteoarthritis Pain scale. Statistical significance was set at a 2-sided Type I error of α = 0.0125 for comparisons at each of the 4 time points. We used a global perceived effect scale to measure patient satisfaction.

RESULTS

The 59 patients (36 female, 23 male) who completed the trial had a mean ± SD age of 68.2 ± 8.6 years. Patients in the active group reported improvements in pain scores at 2, 4, 8, and 12 weeks with a diminution of the effect over time. VAS scores at baseline and at weeks 2, 4, 8, and 12 in the active group (n = 31) versus placebo group (n = 28) were 6.2 versus 5.3 (P = 0.294), 2.7 versus 4.7 (P < 0.001), 3.2 versus 5.1 (P < 0.001), 3.9 versus 4.9 (P < 0.001), and 4.6 versus 5.1 (P = 0.055), respectively. Total WOMAC scores at baseline and at weeks 2, 4, 6, 8, and 12 in the active group versus the placebo group were 54.5 versus 48.1 (P = 0.177), 32.9 versus 44.4 (P < 0.001), 33.7 versus 45.8 (P < 0.001), 39.2 versus 44.8 (P = 0.001), and 42.65 versus 45.1 (P = 0.012), respectively.

CONCLUSION

GNB offers short-term pain relief for knee osteoarthritis.

Small Synthetic Hyaluronan Disaccharide BIS014 Mitigates Neuropathic Pain in Mice

Neuropathic pain (NP) is a challenging condition to treat, as the need for new drugs to treat NP is an unmet goal. We investigated the analgesic potential of a new sulfated disaccharide compound, named BIS014. Oral administration (p.o.) of this compound induced ameliorative effects in formalin-induced nociception and capsaicin-induced secondary mechanical hypersensitivity in mice, but also after partial sciatic nerve transection (spared nerve injury), chemotherapy (paclitaxel)-induced NP, and diabetic neuropathy induced by streptozotocin. Importantly, BIS014, at doses active on neuropathic hypersensitivity (60 mg/kg/p.o.), did not alter exploratory activity or motor coordination (in the rotarod test), unlike a standard dose of gabapentin (40 mg/kg/p.o.) which although inducing antiallodynic effects on the NP models, it also markedly decreased exploration and motor coordination. In docking and molecular dynamic simulation studies, BIS014 interacted with TRPV₁, a receptor involved in pain transmission where it behaved as a partial agonist. Additionally, similar to capsaicin, BIS014 increased cytosolic Ca²⁺ concentration ([Ca²⁺]_c) in neuroblastoma cells expressing TRPV₁ receptors; these elevations were blocked by ruthenium red. BIS014 did not block capsaicin-elicited [Ca²⁺]_c transients, but inhibited the increase in the firing rate of action potentials in bradykinin-sensitized dorsal root ganglion neurons stimulated with capsaicin. Perspective: We report that the oral administration of a new sulfated disaccharide compound, named BIS014, decreases neuropathic pain from diverse etiology in mice. Unlike the comparator gabapentin, BIS014 does not induce sedation. Thus, BIS014 has the potential to become a new efficacious non-sedative oral medication for the treatment of neuropathic pain.

Therapeutic exercise interventions in rat models of arthritis

Arthritis is the leading cause of musculoskeletal pain and disability worldwide. Nearly 50% of individuals over the age of 65 have arthritis, which contributes to limited function, articular pain, physical inactivity, and diminished quality of life. Therapeutic exercise is often recommended in clinical settings for patients experiencing arthritic pain, however, there is little practical guidance regarding the use of therapeutic exercise to alleviate arthritic musculoskeletal pain. Rodent models of arthritis allow researchers to control experimental variables, which cannot be done with human participants, providing an opportunity to test therapeutic approaches in preclinical models. This literature review provides a summary of published findings in therapeutic exercise interventions in rat models of arthritis as well as gaps in the existing literature. We reveal that preclinical research in this field has yet to adequately investigate the impact of experimental variables in therapeutic exercise including their modality, intensity, duration, and frequency on joint pathophysiology and pain outcomes.

Can radiological findings detect neuropathic pain in patients with osteoarthritis of the knee undergoing surgery?

OBJECTIVES

The mechanism underlying neuropathic pain (NP) in osteoarthritis (OA) of the knee is not completely understood. This study aimed to investigate whether possible NP in patients with knee OA undergoing knee surgery is associated with specific radiological findings.

METHODS

This study included 197 patients who underwent knee surgery for symptomatic knee OA. Clinical evaluation was performed using the Central Sensitization Inventory (CSI), Western Ontario and McMaster Universities Arthritis Index (WOMAC), and PainDETECT questionnaire. Radiological evaluation was performed using the hip-knee-ankle (HKA) angle, posterior tibial slope (PTS), varus and valgus laxities, and magnetic resonance imaging OA Knee Score (MOAKS). Radiological findings were compared between patients with possible and unlikely NP. Logistic regression analysis was performed to identify the predictive factors for NP.

RESULTS

There were 163 and 34 patients with unlikely NP and with possible NP, respectively. The percentage of patients with CSI score ≥ 40 was significantly higher in the possible NP group than in the unlikely NP group (17.6% vs. 6.1%). Patients with possible NP had worse WOMAC scores than patients with unlikely NP. There were no significant positive associations between the possible NP and radiological findings in knee OA. Regression analysis showed no predictive factors for possible NP.

CONCLUSIONS

Possible NP is not associated with specific radiological findings in knee OA. Patients with possible NP may mediate CS and experience more severe symptoms, including decreased knee function and lower quality of life, than patients with unlikely NP.

Agmatine Administration Effects on Equine Gastric Ulceration and Lameness

Osteoarthritis (OA) accounts for up to 60% of equine lameness. Agmatine, a decarboxylated arginine, may be a viable option for OA management, based on reports of its analgesic properties. Six adult thoroughbred horses, with lameness attributable to thoracic limb OA, received either daily oral phenylbutazone (6.6 mg/kg), agmatine sulfate (25 mg/kg) or a control for 30 days, with 21-day washout periods between treatments. Subjective lameness, thoracic limb ground reaction forces (GRF), plasma agmatine and agmatine metabolite levels were evaluated using an established rubric, a force platform, and mass spectrometry, respectively, before, during and after each treatment period. Gastric ulceration and plasma chemistries were evaluated before and after treatments. Braking GRFs were greater after 14 and 29 days of agmatine compared to phenylbutazone administration. After 14 days of phenylbutazone administration, vertical GRFs were greater than for agmatine or the control. Glandular mucosal ulcer scores were lower after agmatine than phenylbutazone administration. Agmatine plasma levels peaked between 30 and 60 min and were largely undetectable by 24 h after oral administration. In contrast, plasma citric acid levels increased throughout agmatine administration, representing a shift in the metabolomic profile. Agmatine may be a viable option to improve thoracic limb GRFs while reducing the risk of glandular gastric ulceration in horses with OA.

The impact of waiting time for orthopaedic consultation on pain levels in individuals with osteoarthritis: a systematic review and meta-analysis

OBJECTIVE

Time spent waiting for access to orthopaedic specialist health services has been suggested to result in increased pain in individuals with osteoarthritis (OA). We assessed whether time spent on an orthopaedic waiting list resulted in a detrimental effect on pain levels in patients with knee or hip OA.

METHODS

We searched Ovid MEDLINE, EMBASE and EBSCOhost databases from inception until September 2021. Eligible articles included individuals with OA on an orthopaedic waitlist and not receiving active treatment, and reported pain measures at two or more time points. Random-effects meta-analysis was used to estimate the pooled effect of waiting time on pain levels. Meta-regression was used to determine predictors of effect size.

RESULTS

Thirty-three articles were included (n = 2,490 participants, 67 ± 3 years and 62% female). The range of waiting time was 2 weeks to 2 years (20.8 ± 18.8 weeks). There was no significant change in pain over time (effect size = 0.082, 95% CI = -0.009, 0.172), nor was the length of time associated with longitudinal changes in pain over time (β = 0.004, 95% CI = -0.005, 0.012). Body mass index was a significant predictor of pain (β = -0.043, 95% CI = -0.079, 0.006), whereas age and sex were not.

CONCLUSIONS

Pain remained stable for up to 1 year in patients with OA on an orthopaedic waitlist. Future research is required to understand whether pain increases in patients waiting longer than 1 year.

Pterostilbene improves CFA-induced arthritis and peripheral neuropathy through modulation of oxidative stress, inflammatory cytokines and neurotransmitters in Wistar rats

Pterostilbene is a stilbene flavonoid that occurs naturally in various plants as well as produced by genetic engineering. It exhibits anti-inflammatory, analgesic, anti-oxidant and neuroprotective activities. This research was aimed to determine the potential of pterostilbene against arthritis and peripheral neuropathy in Complete Freund's Adjuvant (CFA) induced arthritis. Rat hind paw was injected with 0.1 ml CFA to induce arthritis. Standard control animals received oral methotrexate (3 mg/kg/week). Pterostilbene at 12.5, 25 and 50 mg/kg was given orally to different groups of arthritic rats from day 7-28 for 21 days. Pterostilbene significantly reduced paw diameter and retarded the decrease in body weight of arthritic rats. It profoundly (p < 0.05-0.0001) reduced lipid peroxidation and nitrites, while increased superoxide dismutase (SOD) in the liver tissue. Pterostilbene treatment significantly (p < 0.0001) reduced TNF-α and IL-6 levels. Pterostilbene markedly improved (p < 0.05-0.001) motor activity and showed analgesic effect in arthritic rats at 25 and 50 mg/kg as compared to disease control rats. Furthermore, it notably (p < 0.05-0.0001) increased SOD activity, nitrites, noradrenaline and serotonin levels in the sciatic nerve of arthritic rats. Treatment with pterostilbene also ameliorated the CFA-induced pannus formation, cartilage damage and synovial hyperplasia in the arthritic rat paws. It is determined from the current study that pterostilbene was effective in reducing CFA-induced arthritis in rats through amelioration of oxidative stress and inflammatory mediators. It was also effective to treat peripheral neuropathy through modulation of oxidative stress and neurotransmitters in sciatic nerves.

Analgesic dorsal root ganglion field stimulation blocks both afferent and efferent spontaneous activity in sensory neurons of rats with monosodium iodoacetate-induced osteoarthritis

OBJECTIVES

Chronic joint pain is common in patients with osteoarthritis (OA). Non-steroidal anti-inflammatory drugs and opioids are used to relieve OA pain, but they are often inadequately effective. Dorsal root ganglion field stimulation (GFS) is a clinically used neuromodulation approach, although it is not commonly employed for patients with OA pain. GFS showed analgesic effectiveness in our previous study using the monosodium iodoacetate (MIA) - induced OA rat pain model. This study was to evaluate the mechanism of GFS analgesia in this model.

METHODS

After osteoarthritis was induced by intra-articular injection of MIA, pain behavioral tests were performed. Effects of GFS on the spontaneous activity (SA) were tested with in vivo single-unit recordings from teased fiber saphenous nerve, sural nerve, and dorsal root.

RESULTS

Two weeks after intra-articular MIA injection, rats developed pain-like behaviors. In vivo single unit recordings from bundles teased from the saphenous nerve and third lumbar (L3) dorsal root of MIA-OA rats showed a higher incidence of SA than those from saline-injected control rats. GFS at the L3 level blocked L3 dorsal root SA. MIA-OA reduced the punctate mechanical force threshold for inducing AP firing in bundles teased from the L4 dorsal root, which reversed to normal with GFS. After MIA-OA, there was increased retrograde SA (dorsal root reflex), which can be blocked by GFS.

CONCLUSIONS

These results indicate that GFS produces analgesia in MIA-OA rats at least in part by producing blockade of afferent inputs, possibly also by blocking efferent activity from the dorsal horn.

Efficacy and safety of tanezumab, NSAIDs, and placebo in patients with moderate to severe hip or knee osteoarthritis and a history of depression, anxiety, or insomnia: post-hoc analysis of phase 3 trials

Objective: Treatment outcomes for chronic pain can be poor in patients with depression, anxiety, or insomnia. This analysis evaluated the efficacy and safety of subcutaneous tanezumab, nonsteroidal anti-inflammatory drugs (NSAIDs), and placebo in patients with osteoarthritis (OA) and a history of these conditions using data from three phase 3 studies.Methods: A post-hoc analysis of data from two pooled placebo-controlled studies and one NSAID-controlled study of subcutaneous tanezumab. All patients had moderate to severe knee or hip OA that was inadequately controlled with standard-of-care analgesics. Efficacy outcomes were least-squares mean change from baseline to Week 16 in Western Ontario McMaster Universities OA Index (WOMAC) Pain, WOMAC Physical Function, Patient's global assessment of OA, and EQ-5D-5L scores. Results were summarized for patients with and without a history of depression, anxiety, or insomnia at baseline.Results: 1545 patients were treated in the pooled placebo-controlled studies (history of depression, 12%; anxiety, 8%; insomnia, 10%; any, 23%) and 2996 in the NSAID-controlled study (16%, 11%, 13%, 28%, respectively). In groups with positive histories, 38-80% took antidepressant or anxiolytic medications at baseline. Within treatments, largely similar improvements in efficacy outcomes were observed in patients with and without a history of depression, anxiety, or insomnia; the types of treatment-emergent adverse events were similar.Conclusions: Patients with OA and a history of depression, anxiety, or insomnia did not appear to experience reduced efficacy outcomes or an altered safety profile in response to tanezumab or NSAID treatment as compared with those without. NCT02697773; NCT02709486; NCT02528188.

A Randomised Controlled Trial of YOGa and Strengthening Exercise for Knee OsteoArthritis: Protocol for a Comparative Effectiveness Trial (YOGA Trial)

Osteoarthritis (OA) is a common joint disorder for which there is no cure. Current treatments are suboptimal. Exercise is a core treatment for knee OA, with muscle strengthening exercise commonly recommended. Yoga is a mind-body exercise intervention that can improve flexibility, muscle strength, balance, and fitness and potentially reduce symptoms of OA. However, there is a scarcity of robust, high-quality conclusive evidence on the efficacy of yoga in knee OA. We are currently conducting the first randomised comparative effectiveness and cost-effectiveness trial of a yoga program compared with a strengthening exercise program in patients with symptomatic knee OA. This study protocol describes the design and conduct of this trial. The YOGA study is a phase III, single-centre, parallel, superiority, randomised, active-controlled trial which will be conducted in Hobart, Australia. One hundred and twenty-six participants (63 in each arm) aged over 40 years with symptomatic knee OA will be recruited from the community and randomly allocated to receive either a 24-week yoga program (3×/week) or a strengthening exercise program (3×/week). The primary outcome will be change in knee pain over 12 weeks, assessed using a 100 mm visual analogue scale (VAS). The secondary outcomes include change in knee pain, patient global assessment, physical function, quality of life, gait speed, biomarkers, and others over 12 and 24 weeks. We will also assess whether the presence of neuropathic pain moderates the effects of yoga compared to strengthening exercise. Additional data, such as cost and resource utilization, will be collected for the cost-effectiveness analysis. The primary analysis will be conducted using an intention-to-treat approach. Adverse events will be monitored throughout the study. Once completed, this trial will contribute to the knowledge of whether yoga can be used as a simple, effective, low-cost option for the management of knee OA, thus saving economic costs in the healthcare system.

Different Prevalence of Neuropathic Pain and Risk Factors in Patients with Knee Osteoarthritis at Stages of Outpatient, Awaiting and after Total Knee Arthroplasty

Objective

Neuropathic pain (NP) plays an important role in patients with knee osteoarthritis (KOA). However, the prevalence of NP at different treatment stages including outpatient, awaiting and after total knee arthroplasty (TKA) have not been compared. The understanding of this issue and identify risk factors can help physicians develop individualized strategies to manage the pain of KOA. Therefore, the aim of the study is to investigate the prevalence and risk factors of NP at different treatment stages of KOA.

Methods

Patients diagnosed as KOA between August 2016 and August 2020 were enrolled in this cross‐sectional study and divided into three groups according to treatment stage, including outpatient stage, awaiting TKA stage (pre‐TKA) and after TKA stage (post‐TKA). A numeric rating scale (NRS) and PainDETECT questionnaire were used to evaluate nociceptive pain and NP. Patient demographics, radiological assessments using Kellgren–Lawrence (K‐L) grade, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were analyzed. Data analysis and statistics were processed using SPSS 20.0 and examined by ANOVA with/without Bonferroni correction or Kruskal–Wallis test. A chi‐square test was used to determine cross‐table data and calculate the odds ratio (OR) value.

Results

Of the 921 patients, the prevalence of possible and likely NP was 17.5% (56/320) and 2.5% (8/320) in the pre‐TKA group compared with 3.4% (8/233) and 0.4% (1/233) in the outpatient group and 1.4% (5/368) and 0.5% (2/368) in the post‐TKA group, respectively. In the pre‐TKA group, higher NRS (NRS >3; OR = 10.65, 95% CI: 3.25–34.92, P < 0.001) and WOMAC pain score (score > 10; OR = 4.88, 95% CI: 2.38–10.01, P < 0.001) conferred an increased risk of unclear pain. Age, gender, BMI and K‐L grade showed no significant differences among the unlikely, possible and likely NP groups.

Conclusion

Prevalence of NP is different at stages of out‐patient, awaiting and after TKA in patients with KOA. Patients awaiting TKA have the highest prevalence of NP compared with patients in outpatient and post‐TKA groups. In the patients waiting for TKA, higher NRS (NRS >3) and WOMAC pain scores (score > 10) are risk factors of NP.

Cannabinoid receptors are expressed in equine synovium and upregulated with synovitis

BACKGROUND

Osteoarthritis (OA) is a major cause of equine lameness. Cannabinoid receptors (CB) are now considered to be promising therapeutic targets in human rheumatology for pain and inflammation, however little is known about the equine endocannabinoid system.

OBJECTIVES

The primary goal was to assess the presence and expression pattern of CB1 and CB2 in the synovium of healthy joints. A secondary goal was to explore the relationship between the CB expression, degree of synovitis and OA pathology.

STUDY DESIGN

Ex vivo experimental study.

METHODS

Metacarpophalangeal joints (n=25) from a tissue bank were studied. The joints were dissected, and the articular cartilage lesions were scored. Synovial membrane specimens (n=45) were harvested, fixed and the degree of synovitis was graded on histological sections. Co-localised synovial sections were also immunostained with antibodies to CB1 and CB2. Five regions of interest (ROIs) were randomly selected from digital images of manually segmented synovial intima and scored blindly for positive cellular immunoreactive staining by 2 independent observers. Interobserver agreement was calculated with an intraclass correlation coefficient (ICC). Relationships between CB1 and CB2 immunoreactive scores and synovitis or joint OA grade were explored with mixed linear models.

RESULTS

CB1 was expressed in synovial intimal cells in all specimens studied whereas CB2 expression was identified in 94%. Both receptors were also expressed in the subintimal blood vessel walls. ICCs were 84.6% (CB1) and 92.9% (CB2) for the immunoreactivity scores. Both CB1 and CB2 expression were significantly upregulated (p=0.04 and p=0.03 respectively) with increasing degree of synovitis. Conversely, CB1 expression significantly decreased (p=0.03) with increasing severity of OA.

MAIN LIMITATIONS

The type of synovial cell expressing CB1 or CB2 was not investigated.

CONCLUSIONS

Equine synovial intimal cells constitutively express both CB1 and CB2 receptors that are upregulated with synovitis and may have a role in joint pain. They are potential targets for therapy with cannabinoid molecules or their derivatives. This article is protected by copyright. All rights reserved.

Trends in Prescriptions for Non-opioid Pain Medications Among U.S. Adults With Moderate or Severe Pain, 2014-2018

As opioid prescribing has declined, it is unclear how the landscape of prescription pain treatment across the U.S. has changed. We used nationally-representative data from the Medical Expenditure Health Survey, 2014 to 2018 to examine trends in prescriptions for opioid and non-opioid pain medications, including acetaminophen, non-steroidal anti-inflammatory drugs, gabapentinoids, and antidepressants among U.S. adults with self-reported pain. Overall, from 2014 to 2018, the percentage of participants receiving a prescription for opioids declined, (38.8% vs 32.8%), remained stable for non-steroidal anti-inflammatory drugs (26.8% vs 27.7%), and increased for acetaminophen (1.6% vs 2.3%), antidepressants (9.6% vs 12.0%) and gabapentinoids (13.2% vs 19.0%). In this period, the adjusted odds of receiving an opioid prescription decreased (aOR = .93, 95% CI = .90-.96), while the adjusted odds of receiving antidepressant, gabapentinoid and acetaminophen prescriptions increased (antidepressants: aOR = 1.08, 95% CI = 1.03-1.13 gabapentinoids: aOR = 1.11, 95% CI = 1.06-1.17; acetaminophen: aOR = 1.10, 95% CI: 1.02-1.20). Secondary analyses stratifiying within the 2014 to 2016 and 2016 to 2018 periods revealed particular increases in prescriptions for gabapentinoids (aOR = 1.13, 95% CI = 1.05-1.21) and antidepressants (aOR = 1.23, 95% CI = 1.12-1.35) since 2016. PERSPECTIVE: These data demonstrate that physicians are increasingly turning to CDC-recommended non-opioid medications for pain management, particularly antidepressants and gabapentinoids. However, evidence for these medications' efficacy in treating numerous common pain conditions, including low back pain, remains limited.

Innate Immunity at the Core of Sex Differences in Osteoarthritic Pain?

Osteoarthritis (OA) is a progressive whole-joint disease; no disease-modifying drugs are currently available to stop or slow its process. Symptoms alleviation is the only treatment option. OA is the major cause of chronic pain in adults, with pain being the main symptom driving patients to seek medical help. OA pathophysiology is closely associated with the innate immune system, which is also closely linked to pain mediators leading to joint pain. Pain research has shown sex differences in the biology of pain, including sexually dimorphic responses from key cell types in the innate immune system. Not only is OA more prevalent in women than in men, but women patients also show worse OA outcomes, partially due to experiencing more pain symptoms despite having similar levels of structural damage. The cause of sex differences in OA and OA pain is poorly understood. This review provides an overview of the involvement of innate immunity in OA pain in joints and in the dorsal root ganglion. We summarize the emerging evidence of sex differences regarding innate immunity in OA pain. Our main goal with this review was to provide a scientific foundation for future research leading to alternative pain relief therapies targeting innate immunity that consider sex differences. This will ultimately lead to a more effective treatment of pain in both women and men.

Pharmacological use of gamma-aminobutyric acid derivatives in osteoarthritis pain management: a systematic review

Background

Pain is the major complication of osteoarthritis (OA) patients and is a decisive symptom for medical intervention. Gamma-aminobutyric acid (GABA) derivatives are optional painkillers but not widely used in pain management of OA patients. We synthesized the efficacy and safety of GABA derivatives for OA pain management.

Methods

We searched Medline, Cochrane CENTRAL, Embase, and ClinicalTrals.gov from inception to 13 October 2021 and included randomized controlled trials (RCTs) comparing the efficacy and safety of GABA derivatives with placebo or standard control in OA pain management. Two independent reviewers extracted data and assessed these studies for risk of bias using Cochrane Collaboration’s tool for RCT.

Results

In total, three eligible RCTs (n = 3) meeting the eligibility criteria were included. Among these RCTs, one focused on hand OA pain management, while two RCTs focused on knee OA. In hand OA, pregabalin reduced numerical rating scale (NRS) score and the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) pain score significantly compared with placebo, and caused 55 AEs. In knee OA, pregabalin reduced visual analogue scale (VAS) score and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain score significantly with no recorded adverse event (AE). Meanwhile, in knee OA, gabapentin reduced both VAS score and WOMAC pain score compared with acetaminophen and caused 9 AEs.

Conclusions

GABA derivatives seem to be effective and safe in OA pain management. However, future researches with large sample size are needed to further prove the efficacy of GABA derivatives in OA pain control.

Trial registration: CRD42021240225.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41927-022-00257-z.

Phenotypic classification of knee osteoarthritis according to pain mechanisms; a clinical observational study

BACKGROUND

Pain in knee osteoarthritis is considered to be nociceptive. Recently, involvement of neuropathic pain and psychosocial factors in knee osteoarthritis has been reported. However, the following details are unclear: 1) How often are neuropathic pain and psychosocial factors involved? And 2) Which patients are associated with neuropathic pain and psychosocial factors?

METHODS

In 104 patients with knee osteoarthritis, we evaluated neuropathic pain factor with a painDETECT questionnaire and catastrophic thinking using the pain catastrophizing scale. Pain intensity was assessed using the visual analog scale; patients with scores below the median were defined as low-pain group and others as high-pain group. Radiographic severity was categorized according to the Kellgren-Lawrence classification, with grades I-II and III-IV defined as low- and high-grades, respectively. We compared the painDETECT and pain catastrophizing scale scores between the low- and high-pain groups and low- and high-grade groups. Furthermore, the painDETECT and pain catastrophizing scale scores were compared among the following four groups: low-grade/low-pain, low-grade/high-pain, high-grade/low-pain, and high-grade/high-pain.

RESULTS

Neuropathic pain factor and catastrophic thinking were found in 16% and 34% of patients, respectively. There were no significant differences in both painDETECT and pain catastrophizing scale scores between the two pain intensity groups. Between the two groups of radiographic severity, there was no significant difference in the painDETECT scores; however, the pain catastrophizing scale score was significantly high in the low-grade group. In addition, there was no significant difference in the painDETECT scores among the four groups; however, the pain catastrophizing scale scores were significantly higher in low-grade/high-pain than in high-grade/low-pain patients.

CONCLUSIONS

Therefore, 64% had only nociceptive pain factor. Catastrophic thinking was strong in patients with low radiographic severity, especially in those with high pain intensity. Patients with neuropathic pain factor could not be identified from radiographic severity and pain intensity.

Voluntary exercise blocks ongoing pain and diminishes bone remodeling while sparing protective mechanical pain in a rat model of advanced osteoarthritis pain

ABSTRACT

Exercise is the most common treatment recommended by healthcare providers for the treatment of musculoskeletal pain. We examined whether voluntary running wheel exercise improves pain and bone remodeling in rats with monosodium iodoacetate-induced unilateral knee joint pain. During acquisition of wheel running before osteoarthritis (OA) treatment, rats separated into 2 groups characterized by either high or low levels of voluntary wheel running as indicated by distance and peak speed. After the induction of knee joint OA, all rats showed diminished voluntary wheel running throughout the study. Voluntary wheel running failed to alter evoked nociceptive responses evaluated as weight asymmetry or hind paw tactile thresholds at any timepoint of the study. By contrast, relief of ongoing pain was demonstrated by conditioned place preference produced by lidocaine injection into the monosodium iodoacetate-treated knee in high but not low-running rats. Both high and low voluntary runners showed diminished trabecular bone loss compared with sedentary controls. These observations indicate that both high-intensity and low-intensity exercise is beneficial in protecting against bone remodeling in advanced OA. The data suggest that similar to clinical observation, bone remodeling does not correlate with pain. In addition, these results suggest that higher intensity exercise may relieve persistent ongoing OA pain while maintaining movement-evoked nociception. The relief of ongoing pain can potentially offer significant improvement in quality of life, whereas preservation of responses to movement-evoked pain may be especially important in protecting the joint from damage because of overuse.

Duloxetine in OsteoArthritis (DOA) study: effects of duloxetine on pain and function in end-stage hip and knee OA – a pragmatic enriched randomized controlled trial

Background

Some osteoarthritis (OA) patients experience inadequate pain relief from analgesics like acetaminophen and nonsteroidal anti-inflammatory drugs. This could be the result of experienced non-nociceptive centralized pain. Placebo-controlled randomized trials (RCT) have proven the effectiveness of duloxetine for OA and several chronic pain conditions where central sensitization (CS) is one of the key underlying pain mechanisms.

Objectives

Assess the efficacy of an 8-week duloxetine treatment compared to usual care in end-stage knee and hip OA patients with a level of centralized pain.

Design

Pragmatic, enriched, open-label RCT.

Methods

Patients were randomized to duloxetine or to care-as-usual. Primary outcome was pain in the index joint, measured with the pain domain of the Knee injury and Osteoarthritis Outcome Score (KOOS) or the Hip disability and Osteoarthritis Outcome Score (HOOS). The intention-to-treat principle was used, with mixed-model repeated measures to analyze the effect.

Results

One hundred eleven patients were randomized. Nearly 44% felt much to very much better after duloxetine usage compared to 0% in the care-as-usual group (p < 0.001). The duloxetine group scored 11.3 points (95%CI: 5.8, 16.8) better on the pain domain of the KOOS/HOOS (p < 0.001). Knee patients improved significantly more than hip patients (18.7 [95%CI: 11.3, 26.1] versus 6.0 [95%CI: − 2.6, 14.5] points better).

Conclusions

Adding duloxetine treatment seems to be beneficial for end-stage knee OA patients with neuropathic-like symptoms (at risk of CS). End stage Hip OA patients seem to be nonresponsive to duloxetine.

Trial registration

Dutch Trial Registry with number NTR 4744 (15/08/2014) and in the EudraCT database with number 2013–004313-41.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05034-0.