Pain sensation in human osteoarthritic knee joints is strongly enhanced by diabetes mellitus

Pain mechanistic networks: the development using supervised multivariate data analysis and implications for chronic pain

ABSTRACT

Chronic postoperative pain is present in approximately 20% of patients undergoing total knee arthroplasty. Studies indicate that pain mechanisms are associated with development and maintenance of chronic postoperative pain. The current study assessed pain sensitivity, inflammation, microRNAs, and psychological factors and combined these in a network to describe chronic postoperative pain. This study involved 75 patients with and without chronic postoperative pain after total knee arthroplasty. Clinical pain intensity, Oxford Knee Score, and pain catastrophizing were assessed as clinical parameters. Quantitative sensory testing was assessed to evaluate pain sensitivity and microRNAs, and inflammatory markers were likewise analyzed. Supervised multivariate data analysis with "Data Integration Analysis for Biomarker Discovery" using Latent cOmponents (DIABLO) was used to describe the chronic postoperative pain intensity. Two DIABLO models were constructed by dividing the patients into 3 groups or 2 defined by clinical pain intensities. Data Integration Analysis for Biomarker discovery using Latent cOmponents model explained chronic postoperative pain and identified factors involved in pain mechanistic networks among assessments included in the analysis. Developing models of 3 or 2 patient groups using the assessments and the networks could explain 81% and 69% of the variability in clinical postoperative pain intensity. The reduction of the number of parameters stabilized the models and reduced the explanatory value to 69% and 51%. This is the first study to use the DIABLO model for chronic postoperative pain and to demonstrate how different pain mechanisms form a pain mechanistic network. The complex model explained 81% of the variability of clinical pain intensity, whereas the less complex model explained 51% of the variability of clinical pain intensity.

The role of the immune system in osteoarthritis: mechanisms, challenges and future directions

Osteoarthritis (OA) is a chronic joint disease that has long been considered a simple wear-and-tear condition. Over the past decade, research has revealed that various inflammatory features of OA, such as low-grade peripheral inflammation and synovitis, contribute substantially to the pathophysiology of the disease. Technological advances in the past 5 years have revealed a large diversity of innate and adaptive immune cells in the joints, particularly in the synovium and infrapatellar fat pad. Notably, the presence of synovial lymphoid structures, circulating autoantibodies and alterations in memory T cell and B cell populations have been documented in OA. These data indicate a potential contribution of self-reactivity to the disease pathogenesis, blurring the often narrow and inaccurate line between chronic inflammatory and autoimmune diseases. The diverse immune changes associated with OA pathogenesis can vary across disease phenotypes, and a better characterization of their underlying molecular endotypes will be key to stratifying patients, designing novel therapeutic approaches and ultimately ameliorating treatment allocation. Furthermore, examining both articular and systemic alterations, including changes in the gut-joint axis and microbial dysbiosis, could open up novel avenues for OA management.

Synovial fluid glycoproteome profiling in knee osteoarthritis: Molecular insights into type 2 diabetes-associated biomarkers and therapeutic targets

Type 2 diabetes mellitus (T2DM) and Osteoarthritis (OA) share common risk factors like age, obesity and hypertension. Currently, 52 % of diabetic patients suffer from arthritis. Diabetes facilitates OA by altering lipid metabolism, levels of adipokines & cytokines, accumulation of advanced glycation end products, etc., which affects cartilage & bone health. However, the molecular mechanisms of the association of OA with T2DM remain unexplored. Since diabetes greatly affects the glycosylation status of proteins, the present study focused on identifying glycoproteins that could serve as diagnostic and prognostic markers for identifying osteoarthritis in diabetic individuals by LC-MS/MS. Comparative proteomic analysis revealed 20 significantly altered glycoproteins; among them, thyroxine-binding globulin (THBG), alpha-1-antitrypsin (A1AT), fibrinogen gamma chain (FGG) and angiotensinogen (AGT) were further validated. THBG, A1AT and AGT showed promising potential to identify the comorbid condition in serum and synovial fluid, however, ROC analysis identified THBG as the best candidate glycoprotein marker. Upregulation of THBG in OADM disrupts the bone remodeling cycle, degrades insulin, and promotes the expression of GLUT-1 and MMP-9. Overall, THBG could also serve as a therapeutic target for reducing the progression of osteoarthritis and alleviating pain and bone stiffness associated with the disease.

Metabolism-Related Adipokines and Metabolic Diseases: Their Role in Osteoarthritis

Osteoarthritis (OA) affects several joints but tends to be more prevalent in those that are weight-bearing, such as the knees, which are the most heavily loaded joints in the body. The incidence and disability rates of OA have continued to increase and seriously jeopardise the quality of life of middle-aged and older adults. However, OA is more than just a wear and tear disease; its aetiology is complex, and its pathogenesis is poorly understood. Metabolic syndrome (MetS) has emerged as a critical driver of OA development. This condition contributes to the formation of a distinct phenotype, termed metabolic syndrome-associated osteoarthritis (MetS-OA),which differs from other metabolically related diseases by its unique pathophysiological mechanisms and clinical presentation. As key mediators of MetS, metabolic adipokines such as leptin, lipocalin, and resistin regulate inflammation and bone metabolism through distinct or synergistic signaling pathways. Their modulation of inflammatory responses and bone remodeling processes plays a critical role in the pathogenesis and progression of OA. Due to their central role in regulating inflammation and bone remodeling, metabolic adipokines not only deepen our understanding of MetS-OA pathogenesis but also represent promising targets for novel therapeutic strategies that could slow disease progression and improve clinical outcomes in affected patients.

Identification and validation of up-regulated TNFAIP6 in osteoarthritis with type 2 diabetes mellitus

Lines of evidence have indicated that type 2 diabetes mellitus (T2DM) is an independent risk factor for osteoarthritis (OA) progression. However, the study focused on the relationship between T2DM and OA at the transcriptional level remains empty. We downloaded OA- and T2DM-related bulk RNA-sequencing and single-cell RNA sequencing data from the Gene Expression Omnibus (GEO) dataset. Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were performed to screen out hub genes between OA and T2DM, and functional enrichment was done. Single-cell sequencing analysis was further used to screen key genes on OA and T2DM datasets. Rat chondrocytes and human articular cartilage were used to validate biomarkers among OA and T2DM. Sixty-eight hub genes were obtained, which were mainly enriched in the inflammatory response. We found that the hub gene TNFAIP6 is not only closely related to OA and T2DM but also a marker of prehypertrophic chondrocytes, which are closely related to the progression of OA. TNFAIP6 was found to be significantly elevated in CD14 + monocytes in T2DM patients, and this group of cells can promote inflammation. Validation on rat chondrocytes and human cartilage showed that TNFAIP6 was highly expressed in OA and further increased in the presence of T2DM or high glucose. Our study identified several characteristic modules and hub genes in the pathogenesis of T2DM-induced OA, which may facilitate further investigation of its molecular mechanisms. Up-regulated TNFAIP6 may contribute to OA in patients with T2DM by the recruitment of pro-inflammatory CD14 + monocytes in the OA synovium, which provides a potential target for the diagnosis and treatment of T2DM-associated OA.

Enhanced joint pain in diabetic patients with knee osteoarthritis is associated with increased synovitis, synovial immune cell infiltration, and erythrocyte extravasation

Objective

Diabetes mellitus (DM) is an important risk factor for the development of osteoarthritis (OA), increasing OA progression and OA pain. To gain insight into the underlying mechanisms of how DM exacerbates OA processes and OA pain, this study analyzed histological differences of synovial tissues from non-DM and DM patients with OA and correlated these differences with knee pain severity.

Materials and methods

Synovial tissue was obtained from 12 non-DM and 10 DM patients with advanced knee OA who underwent total knee arthroplasty. Synovial inflammation was assessed using the Synovitis score developed by Krenn. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to assess knee pain intensity and disability in OA patients. The number of mast cells, macrophages, nerve fibers, capillaries, larger vessels and erythrocyte extravasation were analyzed microscopically in histological and immunostained synovial sections from non-DM and DM patients. Association analyses were performed to determine associations between OA knee pain and synovial changes affected by DM.

Results

Synovial tissue from OA patients with DM had a higher synovitis score, more erythrocyte extravasation, and contained higher numbers of mast cells and macrophages compared to non-DM patients. The number of capillaries and vessels in the lining/sublining layer of the synovial tissue was reduced in DM patients. OA patients with DM had more severe knee pain compared to non-DM patients. The KOOS pain score was associated with the synovitis score, the number of tissue macrophages, and the number of mast cells in the synovial tissue (adjusted for age, sex, and BMI). In addition, the erythrocyte extravasation score was associated with the KOOS pain score and with the synovitis score.

Conclusion

The study suggests that increased OA progression and pain severity in patients with DM result from more pronounced synovitis and synovial vascular leakage and increased infiltration of macrophages and mast cells.

Impact of Interleukin-6 Activation and Arthritis on Epidermal Growth Factor Receptor (EGFR) Activation in Sensory Neurons and the Spinal Cord

In tumor cells, interleukin-6 (IL-6) signaling can lead to activation of the epidermal growth factor receptor (EGFR), which prolongs Stat3 activation. In the present experiments, we tested the hypothesis that IL-6 signaling activates EGFR signaling in peripheral and spinal nociception and examined whether EGFR localization and activation coincide with pain-related behaviors in arthritis. In vivo in anesthetized rats, spinal application of the EGFR receptor blocker gefitinib reduced the responses of spinal cord neurons to noxious joint stimulation, but only after spinal pretreatment with IL-6 and soluble IL-6 receptor. Using Western blots, we found that IL-6-induced Stat3 activation was reduced by gefitinib in microglial cells of the BV2 cell line, but not in cultured DRG neurons. Immunohistochemistry showed EGFR localization in most DRG neurons from normal rats, but significant downregulation in the acute and most painful arthritis phase. In the spinal cord of mice, EGFR was highly activated mainly in the chronic phase of inflammation, with localization in neurons. These data suggest that spinal IL-6 signaling may activate spinal EGFR signaling. Downregulation of EGFR in DRG neurons in acute arthritis may limit nociception, but pronounced delayed activation of EGFR in the spinal cord may be involved in chronic inflammatory pain.

Diabetes is associated with longitudinal declined physical performance measures in persons with or at risk of knee osteoarthritis: data from the Osteoarthritis Initiative

BACKGROUND

The primary aim of this study was to longitudinally examine the impact of diabetes mellitus (DM) on physical performance measures including Gait Speed and Chair Stand tests over 8 years of follow-up in people with or at risk of knee osteoarthritis (OA).

DESIGN

A prospective longitudinal study.

SETTING

Multisite community based.

POPULATION

This study included participants with or at risk of knee OA aged from 45 to 79 years from the Osteoarthritis Initiative from baseline to 96 months follow-up.

METHODS

The participants performed physical performance measures using a 20 m Walk Test for Gait Speed and 5 Times Sit To Stand for repeated chair stand test time at baseline and during follow-up visits. Participants were asked about the presence of diabetes mellitus (DM) at baseline and categorized into with or without DM. Generalized estimating equations were utilized with 2 models, one for DM and Gait Speed and the other for DM and Repeated Chair Stand Test after controlling for covariates including age, sex, education, Body Mass Index (BMI), depressive symptoms, physical activity level, baseline number of comorbidities, and baseline Kellgren and Lawrence grades for OA grading for each knee.

RESULTS

A total of 4796 participants were included and categorized into those with DM (N.=362) and without DM (N.=4311) at baseline. Participants with DM at baseline showed significantly declined gait speed (B=-0.048, 95% Confidence Interval [95% CI]: [-0.07, -0.02], P<0.001) and significantly an increased time for repeated chair stand test (B=0.49, 95% CI: [0.08, 0.89], P=0.018) over time when compared to those without DM at baseline, after controlling for covariates.

CONCLUSIONS

DM was associated with negative impact on Gait Speed and Repeated Chair Stand Test time in individuals with or at risk of knee OA. Individuals with knee OA and diabetes who exhibit declining physical performance measures are at risk of functional dependence, reduced quality of life, and complex rehabilitation requirements.

Importance of IL-6 trans-signaling and high autocrine IL-6 production in human osteoarthritic chondrocyte metabolism

OBJECTIVE

Neutralization of Interleukin (IL)-6-signaling by antibodies is considered a promising tool for the treatment of osteoarthritis (OA). To gain further insight into this potential treatment, this study investigated the effects of IL-6-signaling and IL-6 neutralization on chondrocyte metabolism and the release of IL-6-signaling-related mediators by human chondrocytes.

DESIGN

Chondrocytes were collected from 49 patients with advanced knee/hip OA or femoral neck fracture. Isolated chondrocytes were stimulated with different mediators to analyze the release of IL-6, soluble IL-6 receptor (sIL-6R) and soluble gp130 (sgp130). The effect of IL-6 and IL-6/sIL-6R complex as well as neutralization of IL-6-signaling on the metabolism was analyzed.

RESULTS

OA chondrocytes showed high basal IL-6 production and release, which was strongly negatively correlated with the production of cartilage-matrix-proteins. Chondrocytes produced and released sIL-6R and sgp130. The IL-6/sIL-6R complex significantly increased nitric oxide, prostaglandin E2 and matrix metalloproteinase 1 production, decreased Pro-Collagen Type II and mitochondrial ATP production, and increased glycolysis in OA chondrocytes. Neutralization of IL-6-signaling by antibodies did not significantly affect the metabolism of OA chondrocytes, but blocking of glycoprotein 130 (gp130)-signaling by SC144 significantly reduced the basal IL-6 release.

CONCLUSION

Although IL-6 trans-signaling induced by IL-6/sIL-6R complex negatively affects OA chondrocytes, antibodies against IL-6 or IL-6R did not affect chondrocyte metabolism. Since inhibition of gp130-signaling reduced the enhanced basal release of IL-6, interfering with gp130-signaling may ameliorate OA progression because high cellular release of IL-6 correlates with reduced production of cartilage-matrix-proteins.

Impact of diabetes mellitus on osteoarthritis: a scoping review on biomarkers

Osteoarthritis (OA) commonly affects the knee and hip joints and accounts for 19.3% of disability-adjusted life years and years lived with disability worldwide (Refs , ). Early management is important in order to avoid disability uphold quality of life (Ref. ). However, a lack of awareness of subclinical and early symptomatic stages of OA often hampers early management (Ref. ). Moreover, late diagnosis of OA among those with severe disease, at a stage when OA management becomes more complicated is common (Refs , , , ). Established risk factors for the development and progression of OA include increasing age, female, history of trauma and obesity (Ref. ). Recent studies have also drawn a link between OA and metabolic syndrome, which is characterized by insulin resistance, dyslipidaemia and hypertension (Refs , ).

Cross-Sectional and Longitudinal Associations of Comorbidities with Knee Symptoms and Radiographic Abnormalities of Osteoarthritis

INTRODUCTION

This study aimed to investigate the associations of comorbidities with knee symptoms and radiographic abnormalities of osteoarthritis (OA).

METHODS

Participants were from the Osteoarthritis Initiative. Comorbidities were identified at baseline using the modified Charlson Comorbidity Index. For both knees, symptoms were assessed annually from baseline to 48 months using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function scores (rescaled range 0-100), and radiographic abnormalities using the Kellgren-Lawrence (KL, 0-4) grades. The presence of significant pain and functional disability was defined as a WOMAC score of ≥ 25 and ≥ 22, respectively, and radiographic OA (ROA) as KL ≥ 2. An increase of ≥ 9 in WOMAC scores and ≥ 1 in KL grades were defined as symptomatic and radiographic progression, respectively.

RESULTS

Of 3337 participants, 28% and 9% had one and ≥ 2 comorbidities, respectively. The number of comorbidities was associated with the presence of significant functional disability (odds ratios [ORs] 1.15; 1.46) and predicted the progression of both knee pain and functional disability (ORs 1.11; 1.51). For the type of comorbidities, non-OA musculoskeletal diseases were associated with the presence of ROA and significant functional disability (ORs 1.63; 1.82) and showed a trend to predict incident ROA (OR 1.84, 95% confidence interval 1.00-3.38 p = 0.051). Diabetes and kidney diseases were associated with symptomatic progression of OA (ORs 1.38; 2.72).

CONCLUSIONS

Having more comorbidities, especially diabetes and kidney diseases, is associated with symptomatic progression of knee OA. Moreover, non-OA musculoskeletal diseases may be associated with the presence and onset of ROA.

Targeting YAP1-regulated Glycolysis in Fibroblast-Like Synoviocytes Impairs Macrophage Infiltration to Ameliorate Diabetic Osteoarthritis Progression

The interplay between immune cells/macrophages and fibroblast-like synoviocytes (FLSs) plays a pivotal role in initiating synovitis; however, their involvement in metabolic disorders, including diabetic osteoarthritis (DOA), is largely unknown. In this study, single-cell RNA sequencing (scRNA-seq) is employed to investigate the synovial cell composition of DOA. A significant enrichment of activated macrophages within eight distinct synovial cell clusters is found in DOA synovium. Moreover, it is demonstrated that increased glycolysis in FLSs is a key driver for DOA patients' synovial macrophage infiltration and polarization. In addition, the yes-associated protein 1 (YAP1)/thioredoxin-interacting protein (TXNIP) signaling axis is demonstrated to play a crucial role in regulating glucose transporter 1 (GLUT1)-dependent glycolysis in FLSs, thereby controlling the expression of a series of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) which may subsequently fine-tune the infiltration of M1-polarized synovial macrophages in DOA patients and db/db diabetic OA mice. For treatment, M1 macrophage membrane-camouflaged Verteporfin (Vt)-loaded PLGA nanoparticles (MVPs) are developed to ameliorate DOA progression by regulating the YAP1/TXNIP signaling axis, thus suppressing the synovial glycolysis and the infiltration of M1-polarized macrophages. The results provide several novel insights into the pathogenesis of DOA and offer a promising treatment approach for DOA.

Association between High HbA1c Levels and Mast Cell Phenotype in the Infrapatellar Fat Pad of Patients with Knee Osteoarthritis

Diabetes mellitus (DM) has been suggested as a potential risk factor for knee osteoarthritis (KOA), and its underlying mechanisms remain unclear. The infrapatellar fat pad (IPFP) contributes to OA through inflammatory mediator secretion. Mast cells' (MCs) role in diabetic IPFP pathology is unclear. In 156 KOA patients, hemoglobin A1c (HbA1c) was stratified (HbA1c ≥ 6.5, n = 28; HbA1c < 6.5, n = 128). MC markers (TPSB2, CPA3) in IPFP were studied. Propensity-matched cohorts (n = 27 each) addressed demographic differences. MC-rich fraction (MC-RF) and MC-poor fraction (MC-PF) were isolated, comparing MC markers and genes elevated in diabetic skin-derived MC (PAXIP1, ARG1, HAS1, IL3RA). TPSB2 and CPA3 expression were significantly higher in HbA1c ≥ 6.5 vs. <6.5, both before and after matching. MC-RF showed higher TPSB2 and CPA3 expression than MC-PF in both groups. In the HbA1c ≥ 6.5 group, PAXIP1 and ARG1 expression were significantly higher in the MC-RF than MC-PF. However, no statistical difference in the evaluated genes was detected between the High and Normal groups in the MC-RF. Elevated TPSB2 and CPA3 levels in the IPFP of high HbA1c patients likely reflect higher numbers of MCs in the IPFP, though no difference was found in MC-specific markers on a cell-to-cell basis, as shown in the MC-RF comparison. These findings deepen our understanding of the intricate interplay between diabetes and KOA, guiding targeted therapeutic interventions.

[Concept for integrative pain treatment of osteoarthritis of the knee based on the evidence for conservative and complementary therapies]

BACKGROUND

Osteoarthritis of the knee (gonarthritis) represents a medical challenge.

RESEARCH QUESTION

What is the evidence with respect to approaches of complementary medicine and their integration into multimodal pain management concepts?

MATERIAL AND METHODS

Qualitative nonsystematic literature search on the epidemiology and pathophysiology as well as informative clinical trials, meta-analyses and clinical guidelines about conservative treatment including complementary therapy for gonarthritis.

RESULTS

Osteoarthritis of the knee is a frequent condition with biopsychosocial risks factors for chronification. The German S2k clinical guideline (k = consensus-based, not based on scientific systematic literature searches) published by the Association of the Scientific Medical Societies in Germany (AWMF) in 2017 has not yet been updated. The current guidelines of the American College of Rheumatology (ACR) date from 2020. Both guidelines recommend exercise therapy, weight reduction, short-term analgesics, topical therapy, intra-articular corticoid injections and acupuncture with variable strengths. Furthermore, transcutaneous electrical nerve stimulation (TENS), laser and other electrophysical therapies, shock waves, traction treatment, ergotherapy, comfrey poultices and mudpacks can also be used. Current research supports the benefits of tai chi/qigong and medicinal leaches.

CONCLUSION

Complementary treatment approaches, such as acupuncture, tai chi/qigong, topical naturopathic self-treatment and leeches (with limitations) can, in addition to behavioral changes, exercise therapy and short-term pharmacological treatment, be important evidence-based components of integrative pain management concepts, e.g. in terms of an interdisciplinary multimodal pain treatment (IMPT). Besides pain reduction and functional improvement they promote the internal control conviction through the possibility of self-treatment and self-exercise.

Hypertension Is Associated with Joint Pain Severity Among Individuals with Osteoarthritis

Previous studies have reported an association between hypertension (HTN) and osteoarthritis (OA). However, limited research has examined the association between HTN and symptoms, such as pain severity, in people with OA. Therefore, the aim was to investigate the prevalence of HTN in individuals with OA and the association between HTN and pain severity in this population. This study was cross-sectional and included participants aged 50 years and older from the community. Demographic data were included and self-reported history of chronic illnesses including diabetes, HTN, cardiovascular disease, dyslipidemia, anemia, osteoporosis, neurological disease, and back pain were obtained. Numerous medications and chronic diseases were included. A subsample of people who self-reported osteoarthritis was included in this study. Pain severity was measured over the past 7 days using a pain numeric rating scale. Multiple linear regression was used after adjusting for covariates. A total of 82 participants with OA were included, and the prevalence of HTN among individuals with OA was 28.91%. Hypertension was significantly associated with increased joint pain severity in this population after adjustments for covariates (B=1.81; 95% CI, 0.65, 2.97; p = .003). Hypertension is prevalent in individuals with OA and is significantly associated with pain severity in this population. Future research should consider the effect of HTN control and medication on symptoms in people with OA. Clinicians may implement screening for HTN among individuals with OA because of the association between HTN and symptoms, such as pain, in this population.

Osteoarthritis and Diabetes: Where Are We and Where Should We Go?

Diabetes mellitus (DM) and osteoarthritis (OA) are chronic noncommunicable diseases that affect millions of people worldwide. OA and DM are prevalent worldwide and associated with chronic pain and disability. Evidence suggests that DM and OA coexist within the same population. The coexistence of DM in patients with OA has been linked to the development and progression of the disease. Furthermore, DM is associated with a greater degree of osteoarthritic pain. Numerous risk factors are common to both DM and OA. Age, sex, race, and metabolic diseases (e.g., obesity, hypertension, and dyslipidemia) have been identified as risk factors. These risk factors (demographics and metabolic disorder) are associated with DM or OA. Other possible factors may include sleep disorders and depression. Medications for metabolic syndromes might be related to the incidence and progression of OA, with conflicting results. Given the growing body of evidence indicating a relationship between DM and OA, it is vital to analyze, interpret, and integrate these findings. Therefore, the purpose of this review was to evaluate the evidence on the prevalence, relationship, pain, and risk factors of both DM and OA. The research was limited to knee, hip, and hand OA.

Predicting pain after standard pain therapy for knee osteoarthritis - the first steps towards personalized mechanistic-based pain medicine in osteoarthritis

OBJECTIVES

The prevalence of osteoarthritis (OA) is rising, and pain is the hallmark symptom of OA. Pain in OA is complicated and can be influenced by multiple joint-related factors and factors related to, e.g., physiological, epigenetic, and pain sensory profiles. Increasing evidence suggests that a subset of patients with OA are pain sensitive. This can be assessed using quantitative sensory testing (QST). Common treatments of OA are total knee arthroplasty (TKA) and administration of 3-weeks of non-steroidal anti-inflammatory drugs (NSAIDs), which provide pain relief to many patients with OA. However, approx. 20% of patients experience chronic postoperative pain after TKA, whereas NSAIDs provide an average pain relief of approx. 25%. The current topical review focuses on the emerging evidence linking pretreatment QST to the treatment response of TKA and NSAID treatments.

CONTENT

MEDLINE was systematically searched for all studies from 2000 to 2022 on pretreatment QST, TKA, and NSAIDs. Pre-clinical studies, reviews, and meta-analyses were excluded.

SUMMARY

Currently, 14 studies on TKA and four studies on NSAIDs have been published with the aim to attempt prediction of the treatment response. The QST methodologies in the studies are inconsistent, but 11/14 (79%) studies on TKA and 4/4 (100%) studies on NSAIDs report statistically significant associations between pretreatment QST and chronic postoperative pain after TKA or analgesic effect after NSAID treatment. The strength of the associations remains low-to-moderate. The most consistent pretreatment QST predictors are pressure pain thresholds, temporal summation of pain, and conditioned pain modulation.

OUTLOOK

The use of QST as predictors of standard OA treatment is interesting, but the predictive strength remains low-to-moderate. A transition of QST from a research-based setting and into the clinic is not advised until the predictive strength has been improved and the methodology has been standardized.

[Impact of lockdown on physical activity of patients with osteoarthritis during the COVID-19 pandemic]

INTRODUCTION

Physical activity is essential in the osteoarthritis population, however, confinement during the COVID pandemic forced lifestyle changes. An observational and descriptive study was conducted to assess physical exercise in people with degenerative osteoarticular disease (DOD) during the COVID-19 pandemic.

MATERIAL AND METHODS

A telephone survey was conducted among people over 60 years of age with DOD previously treated at the Hospital Central de la Cruz Roja, assessing physical exercise during the COVID-19 pandemic confinement. The variables (time of physical exercise, causes if exercise was reduced, and pain intensity) were analysed and compared with the situation prior to home confinement.

RESULTS

A total of 33 patients (8 men, 25 women) were included, with a mean age of 75.6 years. Polyarthrosis was the most frequent diagnosis. 51.5% performed the same amount of physical exercise, 21.21% performed more and 24.2% less than before. Only 6.1% performed more than 1 h a day of activity. 36.4% had more pain than previously.

CONCLUSIONS

Although there is a high adherence to the exercises learned in the rehabilitation service, COVID-19 confinement has had a negative effect on the level of exercise performed by POD patients. It is advisable to encourage physical exercise during periods of lockdown.

Chronic Postoperative Pain after Total Knee Arthroplasty: The Potential Contributions of Synovitis, Pain Sensitization, and Pain Catastrophizing - An Explorative Study

Background

A subset of osteoarthritis patients will experience chronic postoperative pain after total knee arthroplasty (TKA), but the source of pain is unclear. The aim of this exploratory study was to assess patients with and without postoperative pain after TKA using magnetic resonance imaging (MRI), quantitative sensory testing (QST), clinical assessment of pain and assessments of catastrophizing thoughts.

Methods

Forty‐six patients completed the 6‐month postoperative assessment. MRI findings were scored according to the MRI Osteoarthritis Knee Score recommendation for Hoffa synovitis, effusion size and bone marrow lesions. QST included assessment of pressure pain thresholds (PPTs), temporal summation of pain (TSP) and conditioned pain modulation (CPM). Pain catastrophizing was assessed using the Pain Catastrophizing Scale (PCS). Clinical pain assessment was conducted using a visual analogue scale (VAS, 0–10 cm), and groups of moderate‐to‐severe (VAS > 3) and none‐to‐mild postoperative pain (VAS ≤ 3) were identified.

Results

Patients with moderate‐to‐severe postoperative pain (N = 15) demonstrated higher grades of Hoffa synovitis (p < 0.001) and effusion size (p < 0.001), lower PPTs (p = 0.039), higher TSP (p = 0.001) and lower CPM (p = 0.014) when compared with patients with none‐to‐mild postoperative pain (N = 31). No significant difference was found in PCS scores between the two groups. Multiple linear regression models found synovitis (p = 0.036), effusion size (p = 0.003), TSP (p = 0.013) and PCS (p < 0.001) as independent parameters contributing to the postoperative pain intensity.

Conclusion

These exploratory findings could indicate that chronic postoperative pain after TKA is a combination of joint‐related synovitis and effusion, sensitization of central pain mechanisms and potentially pain catastrophizing thoughts, but larger studies are needed to confirm this.

Significance

The end‐stage treatment of knee osteoarthritis is total knee arthroplasty. Some patients experience chronic postoperative pain after total knee arthroplasty, but the mechanism for chronic postoperative pain is widely unknown. The current study indicates that higher levels postoperative of synovitis and effusion, higher temporal summation of pain and higher pain catastrophizing scores could be associated with higher chronic postoperative pain.

Interleukin-6 signaling mediates cartilage degradation and pain in posttraumatic osteoarthritis in a sex-specific manner

Osteoarthritis (OA) and posttraumatic OA (PTOA) are caused by an imbalance in catabolic and anabolic processes in articular cartilage and proinflammatory changes throughout the joint, leading to joint degeneration and pain. We examined whether interleukin-6 (IL-6) signaling contributed to cartilage degradation and pain in PTOA. Genetic ablation of Il6 in male mice decreased PTOA-associated cartilage catabolism, innervation of the knee joint, and nociceptive signaling without improving PTOA-associated subchondral bone sclerosis or chondrocyte apoptosis. These effects were not observed in female Il6^-/- mice. Compared with wild-type mice, the activation of the IL-6 downstream mediators STAT3 and ERK was reduced in the knees and dorsal root ganglia (DRG) of male Il6^-/- mice after knee injury. Janus kinases (JAKs) were critical for STAT and ERK signaling in cartilage catabolism and DRG pain signaling in tissue explants. Whereas STAT3 signaling was important for cartilage catabolism, ERK signaling mediated neurite outgrowth and the activation of nociceptive neurons. These data demonstrate that IL-6 mediates both cartilage degradation and pain associated with PTOA in a sex-specific manner and identify tissue-specific contributions of downstream effectors of IL-6 signaling, which are potential therapeutic targets for disease-modifying OA drugs.

The association between diabetes mellitus and functionality in knee osteoarthritis: a cross-sectional study

Objective: The aim of this study was to determine the roles of diabetes mellitus (DM) on quality of life, function of knee, and muscle strength in patients with knee osteoarthritis (OA). Material and Method: This single-center, case-control study prospectively enrolled outpatients with knee OA visiting a physical therapy and rehabilitation clinic. The patients were grouped according to the presence of DM diagnosis. Demographic data, disease duration, and medical treatments of patients were recorded. Clinical parameters, radiographic grading (Kellgren-Lawrence grades), functional scales of the knee and quality of life were evaluated. Results: The study included 82 participants [age: 61.3±6.7 years; female: 76.8%]. The mean Western Ontario and McMaster Universities Osteoarthritis Index of OA patients with (n=37) and without DM (n=45) were 45.79±18.04 vs. 65.94±16.23, respectively (p=0.003). The Hb A1c levels showed a negative correlation with Knee Injury and Osteoarthritis Outcome Score components (pain, quality of life, sports, daily activities, symptom duration) (p

Osteoarthritis-Induced Metabolic Alterations of Human Hip Chondrocytes

Osteoarthritis (OA) alters chondrocyte metabolism and mitochondrial biology. We explored whether OA and non-OA chondrocytes show persistent differences in metabolism and mitochondrial function and different responsiveness to cytokines and cAMP modulators. Hip chondrocytes from patients with OA or femoral neck fracture (non-OA) were stimulated with IL-1β, TNF, forskolin and opioid peptides. Mediators released from chondrocytes were measured, and mitochondrial functions and glycolysis were determined (Seahorse Analyzer). Unstimulated OA chondrocytes exhibited significantly higher release of IL-6, PGE₂ and MMP1 and lower production of glycosaminoglycan than non-OA chondrocytes. Oxygen consumption rates (OCR) and mitochondrial ATP production were comparable in unstimulated non-OA and OA chondrocytes, although the non-mitochondrial OCR was higher in OA chondrocytes. Compared to OA chondrocytes, non-OA chondrocytes showed stronger responses to IL-1β/TNF stimulation, consisting of a larger decrease in mitochondrial ATP production and larger increases in non-mitochondrial OCR and NO production. Enhancement of cAMP by forskolin prevented IL-1β-induced mitochondrial dysfunction in OA chondrocytes but not in non-OA chondrocytes. Endogenous opioids, present in OA joints, influenced neither cytokine-induced mitochondrial dysfunction nor NO upregulation. Glycolysis was not different in non-OA and OA chondrocytes, independent of stimulation. OA induces persistent metabolic alterations, but the results suggest upregulation of cellular mechanisms protecting mitochondrial function in OA.

Radiological changes in shoulder osteoarthritis and pain sensation correlate with patients’ age

Purpose

Osteoarthritis (OA) is one of the most common musculoskeletal disorders in the aging population. The correlation of radiographic OA severity, disability and pain is variable and inconsistent for the different joints. This study aims to elucidate the relationship between histological and radiological signs of shoulder OA with pain sensation and functional impairment to potentially adapt the recommendation for surgical treatment for primary total shoulder arthroplasty (TSA).

Methods

Forty-four patients with shoulder OA undergoing TSA using an anatomic stemless implant were included in this study. The radiological OA severity was scored pre-operatively on true ap X-rays according to the Kellgren–Lawrence score (KL-Score). Acromial types according to Bigliani were defined by pre-operative radiological images. The histological OA severity was determined according to the OARSI-Score using bone–cartilage sections from loaded areas of the humeral head. Pain was quantified using the visual analog scale (VAS). The functional status was assessed by the items “mobility” and “strength” out of the Constant–Murley score (CS Score). Demographic data including BMI, age, gender, diabetes mellitus and smoking were recorded.

Results

There was no correlation between radiographic and histological severity in shoulder OA. However, a correlation of age and the severity of radiological changes was observed. Further, pain did not correlate with histological or radiological scores, whereas it correlated with age and the presence of diabetes mellitus. The functional shoulder status (mobility, strength) correlated with the severity of radiological changes, but not with the histologic scoring, which correlated with nicotine abuse.

Conclusion

This study shows that increased age is the main determinant of radiological changes in shoulder OA, as well as pain. Therefore, age and pain sensation should be considered as important parameters for the recommendation for TSA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03137-x.

Interactions between diabetes mellitus and osteoarthritis; from animal studies to clinical data

Diabetes mellitus (DM) and osteoarthritis (OA) are commonly known metabolic diseases that affect a large segment of the world population. These two conditions share several risk factors such as obesity and aging; however, there is still no consensus regarding the direct role of DM on OA development and progression. Interestingly, both animal and human studies have yielded conflicting results, with some showing a significant role for DM in promoting OA, while others found no significant interactions between these conditions. In this review, we will discuss preclinical and clinical data that assessed the interaction between DM and OA. We will also discuss possible mechanisms associated with the effect of high glucose on the articular cartilage and chondrocytes. An emerging theme dominates the breath of published work in this area: most of the studies discussed in this review do not take into consideration the role of other factors such as the type of diabetes, age, biological sex, type of animal model, body mass index, and the use of pain medications when analyzing and interpreting data. Therefore, future studies should be more rigorous when designing experiments looking at DM and its effects on OA and should carefully account for these confounding factors, so that better approaches can be developed for monitoring and treating patients at risk of OA and DM. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Continuous care intervention with carbohydrate restriction improves physical function of the knees among patients with type 2 diabetes: a non-randomized study

Background

In a previous study, we assessed a novel, remotely monitored carbohydrate restricted diet regimen including nutritional ketosis in patients with type 2 diabetes and reported significant improvements in weight, glycemic control, abdominal fat and inflammation from baseline to 2 years. Knee outcome measures were collected as a secondary outcome in the trial. This study aims to assess the effect of this intervention on knee functional scores and to identify if changes in weight, central abdominal fat (CAF), glycemic status and high sensitivity C-reactive protein (hsCRP) were associated with its improvement.

Methods

This prospective analysis included continuous care intervention (CCI, n = 173) and usual care (UC, n = 69) trial participants with type 2 diabetes that reported knee pain at baseline. Knee outcome measures included the Knee injury and Osteoarthritis Outcome Score (KOOS) pain, symptoms, activities of daily living (ADL), sports and recreation function, and knee-related quality of life subscales, and total KOOS score were assessed from baseline to 2 years. Missing data at each time point were replaced with multiple imputation under the assumption of missing at random. To assess if the primary analysis of the knee scores changed under plausible missing not at random assumptions, sensitivity analysis was also performed using pattern mixture models. In CCI, we also assessed factors associated with the improvement of knee scores.

Results

In the primary analysis, CCI participants demonstrated a statistically significant improvement in total KOOS and all KOOS individual subscale scores at 1 year and maintained through 2 years as opposed to UC patients who showed no significant changes from baseline to 2 years. The significant improvement in total KOOS and its individual subscale scores from baseline to 2 years remained relatively stable in CCI in the sensitivity analysis under different missing not at random scenarios confirming the robustness of the findings from the primary analysis. Approximately 46% of the CCI participants met the 10 points minimal clinically important change at 2 years. A reduction in CAF was associated with improvement in total KOOS and KOOS ADL, while a decrease in hsCRP was associated with improvement in KOOS symptoms scores.

Conclusion

A very low carbohydrate intervention including nutritional ketosis resulted in significant improvements in knee pain and function among patients with T2D. The improvements in knee function were likely secondary to a reduction in central adiposity and inflammation. Future research on the applicability of this intervention in radiographically confirmed OA patients is important.

Trial registration

Clinical trial registration: NCT02519309 (10/08/2015).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05258-0.

Hyperglycemia-induced accumulation of advanced glycosylation end products in fibroblast-like synoviocytes promotes knee osteoarthritis

Osteoarthritis (OA) is significantly associated with diabetes, but how hyperglycemia induces or aggravates OA has not been shown. The synovium plays a critical role in cartilage metabolism and substance exchange. Herein, we intended to investigate whether and how hyperglycemia affects the occurrence and progression of OA by influencing the synovium. In patients with knee OA and diabetes (DM OA), we found a more severe inflammatory response, higher endoplasmic reticulum stress (ERS) levels, and more advanced glycosylation end products (AGEs) accumulation in the synovium than in patients without diabetes. Subsequently, we found similar results in the DM OA group in a rat model. In the in vitro cocultivation system, high glucose-stimulated AGEs accumulation, ERS, and inflammation in rat fibroblast-like synoviocytes (FLSs), which resulted in chondrocyte degeneration due to inflammatory factors from FLSs. Furthermore, in the synovium of the DM OA group and FLSs treated with high glucose, the expression of glucose transporter 1 (GLUT1) and its regulatory factor hypoxia-inducible factor (HIF)-1α was increased significantly. Inhibitors of HIF-1α, GLUT1 or AGEs receptors attenuated the effect of high glucose on chondrocyte degradation in the FLS-chondrocyte coculture system. In summary, we demonstrated that hyperglycemia caused AGEs accumulation in FLSs via the HIF-1α-GLUT1 pathway, which increases the release of inflammatory factors from FLSs, subsequently inducing chondrocyte degradation and promoting OA progression.

Diabetes Mellitus Is Not a Negative Prognostic Factor for Patients Undergoing Hip Arthroscopy

Diabetes mellitus (DM) has been associated with inferior clinical outcomes and comorbidities in general. The authors sought to compare the outcomes of hip arthroscopy at minimum 2-year follow-up for patients with DM with those of patients without DM. Data were prospectively collected and retrospectively reviewed for patients who underwent hip arthroscopy between February 2008 and December 2014. The inclusion criteria were patients with DM who underwent hip arthroscopy for the treatment of femoroacetabular impingement and labral tears and had preoperative patient- reported outcomes. The exclusion criteria were preoperative Tönnis grade greater than 1, previous ipsilateral hip surgery, and/or previous conditions. All patients with DM were matched in a 1:2 ratio to control patients without DM. The matching criteria were age at surgery, sex, body mass index, workers' compensation, capsular treatment, and acetabular Outerbridge grade 0 or 1 vs 2, 3, or 4. Of 29 eligible patients with DM, 26 (89.7%) had minimum 2-year follow-up. Twenty-six patients with DM were matched and compared with 52 patients without DM. Acetabuloplasty was performed more frequently in the control group (P=.01). There were no other statistically significant differences detected in terms of demographics, preoperative radiographic imaging, intraoperative findings, procedures, preoperative scores, follow-up scores, revision rates, rates of conversion to total hip arthroplasty, or complication rates. Patients with DM demonstrated favorable improvements at 2 or more years after arthroscopic labral treatment when compared with a matched control group without DM. The DM group demonstrated a non-statistically significant trend toward inferior outcomes in all patient-reported outcomes, visual analog scale score, and satisfaction. [Orthopedics. 2021;44(4):241-248.].

Comparison of Postoperative Pain and Analgesia Requirement among Diabetic and Nondiabetic Patients undergoing Lower Limb Fracture Surgery - A Prospective Observational Study

Background:

Diabetic patients usually experience neuropathic pain and have a decreased response to opioids. Fractures are acute conditions and as such, they are very painful. No data is available related to fracture and postoperative pain in diabetics.

Aim:

This study was conducted to evaluate postoperative pain and analgesics requirement among diabetic and nondiabetic patients undergoing lower limb fracture surgery and the effect of glycosylated hemoglobin (HbA1c) on the postoperative pain.

Setting and Design:

This was a prospective observational study, conducted on 80 patients comprising of nondiabetic and diabetic, scheduled for elective lower limb fracture surgery under spinal anesthesia.

Materials and Methods:

HbA1c was done in all the patients who were included in the study. Postoperative Visual Analog Scale (VAS) and analgesic consumption were assessed by an anesthesiologist blinded to the diabetic or nondiabetic status of the patients. VAS was assessed every 2^nd hourly, for 24 h and rescue analgesia was given if the VAS was ≥4 and record was maintained. Sedation scores and adverse effects were also recorded postoperatively.

Statistical Analysis:

The Chi-square test was used for the analysis of categorical variables and Student's t-test was used for continuous variables.

Results:

Diabetic group of patients had a significantly high VAS score with P ≤ 0.05. Rescue analgesics requirement was significantly different in two groups with diabetic patients requiring more supplementation of analgesia with a P = 0.025. The overall patient satisfaction was lesser in diabetic group (P = 0.004). There was statistically significant correlation between glycosylated hemoglobin and VAS at 2^nd, 16^th, 18^th, 20^th, 22^nd, and 24^th h.

Conclusion:

Postoperative pain and analgesic requirement was significantly higher in diabetic patients with lower limb fracture. Glycosylated hemoglobin had good correlation with higher VAS.

Patients With High Chronic Postoperative Knee Pain 5 Years After Total Knee Replacement Demonstrate Low-grad Inflammation, Impairment of Function, and High Levels of Pain Catastrophizing

OBJECTIVES

Total knee replacement (TKR) normally provides improvements of physical function and reduces pain. However, ∼20% of the patients report chronic postoperative knee pain. The aims of the present study were to assess the pain, physical function, and physiological characteristics 5 years after TKR surgery.

MATERIALS AND METHODS

Eighty patients were recruited 5 years after TKR and divided into 2 groups based on their average 24-hour knee pain intensity assessed on a visual analog scale (VAS 0 to 10) ("high pain group": VAS≥3; "low pain group": VAS<3). The patients completed the PainDETECT Questionnaire (PDQ), Oxford Knee Score (OKS), Pain Catastrophizing Scale, and Forgotten Joint Score-12. Furthermore, the patients underwent a clinical examination of the knees and high-sensitivity serum C-reactive protein was measured as an inflammatory marker.

RESULTS

A total of 53% of the patients in the high pain group were not satisfied with the outcome, while only 11% of the patients in the low pain group was not satisfied, and the pain intensities in the 2 groups were 5.1 (4.6 to 5 to 6) and 1.1 (0.6 to 1.5) (P<0.001), respectively. Furthermore, the high pain group demonstrates worse scores in: Forgotten Joint Score-12 (P=0.001), OKS function (P<0.001), OKS pain (P<0.001), and Pain Catastrophizing Scale (P<0.001).The high pain group demonstrated increased level of high-sensitivity serum C-reactive protein (4.3 mg/L [3.2 to 5.5] vs. 1.7 mg/L [1.2 to 2.2], P<0.001), and decreased range of motion in the knee (110 vs. 119-degree range of motion, P=0.013).

DISCUSSION

Patients with high chronic postoperative knee pain 5 years after TKR demonstrate decreased physical function, higher levels of catastrophizing thoughts, and increased levels of inflammation.

MicroRNA-183 attenuates osteoarthritic pain by inhibiting the TGFα-mediated CCL2/CCR2 signalling axis

AIMS

MicroRNA-183 (miR-183) is known to play important roles in osteoarthritis (OA) pain. The aims of this study were to explore the specific functions of miR-183 in OA pain and to investigate the underlying mechanisms.

METHODS

Clinical samples were collected from patients with OA, and a mouse model of OA pain was constructed by surgically induced destabilization of the medial meniscus (DMM). Reverse transcription quantitative polymerase chain reaction was employed to measure the expression of miR-183, transforming growth factor α (TGFα), C-C motif chemokine ligand 2 (CCL2), proinflammatory cytokines (interleukin (IL)-6, IL-1β, and tumour necrosis factor-α (TNF-α)), and pain-related factors (transient receptor potential vanilloid subtype-1 (TRPV1), voltage-gated sodium 1.3, 1.7, and 1.8 (Nav1.3, Nav1.7, and Nav1.8)). Expression of miR-183 in the dorsal root ganglia (DRG) of mice was evaluated by in situ hybridization. TGFα, CCL2, and C-C chemokine receptor type 2 (CCR2) levels were examined by immunoblot analysis and interaction between miR-183 and TGFα, determined by luciferase reporter assay. The extent of pain in mice was measured using a behavioural assay, and OA severity assessed by Safranin O and Fast Green staining. Immunofluorescent staining was conducted to examine the infiltration of macrophages in mouse DRG.

RESULTS

miR-183 was downregulated in tissue samples from patients and mice with OA. In DMM mice, overexpression of miR-183 inhibited the expression of proinflammatory cytokines (IL-6, IL-1β, TNF-α) and pain-related factors (TRPV1, Nav1.3, Nav1.7, Nav1.8) in DRG. OA pain was relieved by miR-183-mediated inhibition of macrophage infiltration, and dual luciferase reporter assay demonstrated that miR-183 directly targeted TGFα.

CONCLUSION

Our data demonstrate that miR-183 can ameliorate OA pain by inhibiting the TGFα-CCL2/CCR2 signalling axis, providing an excellent therapeutic target for OA treatment. Cite this article: Bone Joint Res 2021;10(8):548-557.

Serum Inflammatory Markers in Patients With Knee Osteoarthritis: A Proteomic Approach

OBJECTIVES

Osteoarthritis (OA) is known to be a slowly progressive disease that alters all tissue compartments of the joint involved with a characteristic degradation of the cartilage, bone remodeling, and inflammation. One of the prominent symptoms in OA patients is pain, but a few radiologic, inflammatory, or structurally related biomarkers have shown few if any associations with pain. This study aimed to assess serum levels of 92 markers involved in inflammatory pathways in patients with knee osteoarthritis (KOA) and evaluate their possible associations with the clinical pain intensity.

MATERIALS AND METHODS

Serum samples were collected from 127 KOA patients and 39 healthy participants with no knee pain. Each serum sample was analyzed for 92 inflammatory markers using the Proximity Extension Array (PEA) technology. Clinical pain intensity was assessed using a Visual Analog Scale, and patients completed the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire.

RESULTS

Fifteen markers were significantly different when comparing KOA patients and healthy participants. Two markers, fibroblast growth factor-21 and Eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), correlated positively with pain intensity (R=0.235, P=0.008; R=0.233, P=0.008). Moreover, a linear regression model showed interleukin-6, macrophage colony-stimulating factor 1, fibroblast growth factor-21, and tumor necrosis factor superfamily member 12 (TWEAK) as significant independent parameters for pain intensity.

DISCUSSION

The associations between specific cytokines and KOA pain intensities provide new insights into the understanding of the underlying factors driving the pain in OA.

The predictive value of quantitative sensory testing: a systematic review on chronic postoperative pain and the analgesic effect of pharmacological therapies in patients with chronic pain

Studies have suggested that quantitative sensory testing (QST) might hold a predictive value for the development of chronic postoperative pain and the response to pharmacological interventions. This review systematically summarizes the current evidence on the predictive value of QST for chronic postoperative pain and the effect of pharmacological interventions. The main outcome measures were posttreatment pain intensity, pain relief, presence of moderate-to-severe postoperative pain, responders of 30% and 50% pain relief, or validated questionnaires on pain and disability. A systematic search of MEDLINE and EMBASE yielded 25 studies on surgical interventions and 11 on pharmacological interventions. Seventeen surgical and 11 pharmacological studies reported an association between preoperative or pretreatment QST and chronic postoperative pain or analgesic effect. The most commonly assessed QST modalities were pressure stimuli (17 studies), temporal summation of pain (TSP, 14 studies), and conditioned pain modulation (CPM, 16 studies). Of those, the dynamic QST parameters TSP (50%) and CPM (44%) were most frequently associated with chronic postoperative pain and analgesic effects. A large heterogeneity in methods for assessing TSP (n = 4) and CPM (n = 7) was found. Overall, most studies demonstrated low-to-moderate levels of risk of bias in study design, attrition, prognostic factors, outcome, and statistical analyses. This systematic review demonstrates that TSP and CPM show the most consistent predictive values for chronic postoperative pain and analgesic effect, but the heterogeneous methodologies reduce the generalizability and hence call for methodological guidelines.

Type 2 Diabetes Affects Joint Pain Severity in People with Localized Osteoarthritis: A Retrospective Study

OBJECTIVE

To examine the association between type 2 diabetes (T2D) and pain severity in people with localized osteoarthritis (OA) and to explore the association between glycemic control, measured by hemoglobin A1c (HbA1c) level, and pain severity in people with localized OA and T2D.

DESIGN

Retrospective study.

SETTING

A tertiary medical center.

SUBJECTS

Data from 819 patients (mean age = 65.08±9.77 years, 54.3% women) were used.

METHODS

Patients were grouped to localized OA only (N = 671) and localized OA+T2D (N = 148) based on diagnosis codes. An index date was set as the first diagnosis date of localized OA and linked to pain severity, measured by numeric rating scale from 0 to 10. HbA1c values were obtained for patients with T2D within six months of the index date. Multiple linear regression was used.

RESULTS

After controlling for age, gender, body mass index (BMI); diagnoses of depression, hypertension, dyslipidemia; OA locations; and medication list (+/- 90 days of the index date), T2D was significantly associated with increased pain severity (B = 1.07, 95% confidence interval [CI] = 0.25 to 1.88, P = 0.014). For patients with T2D and localized OA with available data for HbA1c (N = 87), the results showed that an increased HbA1c value was significantly associated with higher pain severity (B = 0.36, 95% CI = 0.036 to 0.67, P = 0.029) after controlling for age, gender, BMI, medications, and OA locations.

CONCLUSION

T2D was associated with higher pain severity in people with localized OA, and poor glycemic control was associated with higher pain severity in people with localized OA+T2D. Clinicians should emphasize that better HbA1c control might help with pain management in people with T2D and OA.

Gait Speed as a Predictor for Diabetes Incidence in People with or at Risk of Knee Osteoarthritis: A Longitudinal Analysis from the Osteoarthritis Initiative

BACKGROUND

This study examined the association between baseline gait speed with incident diabetes mellitus (DM) among people with or at elevated risk for knee OA.

MATERIALS AND METHODS

Participants from the Osteoarthritis Initiative, aged 45 to 79 years, where included. Participants with or at risk of knee OA from baseline to the 96-month visit were included. Participants with self-reported DM at baseline were excluded. DM incidence was followed over the 4-time points. Gait speed was measured at baseline using a 20-m walk test. Generalized estimating equations with logistic regression were utilized for analyses. Receiver operator characteristic curves and area under the curve were used to determine the cutoff score for baseline speed.

RESULTS

Of the 4313 participants included in the analyses (58.7% females), 301 participants had a cumulative incidence of DM of 7.0% during follow-up. Decreased gait speed was a significant predictor of incident DM (RR 0.44, p = 0.018). The threshold for baseline gait speed that predicted incident DM was 1.32 m/s with an area under the curve of 0.59 (p < 0.001).

CONCLUSIONS

Baseline gait speed could be an important screening tool for identifying people at risk of incident diabetes, and the determined cutoff value for gait speed should be examined in future research.

Impact of Diabetes Mellitus on Knee Osteoarthritis Pain and Physical and Mental Status: Data From the Osteoarthritis Initiative

OBJECTIVE

Diabetes mellitus (DM) appears to increase osteoarthritic knee pain, which may be related to greater adiposity and more advanced disease status often observed in individuals with osteoarthritis (OA) and DM. We aimed to assess whether OA knee pain and health status are worse in individuals with OA and DM, independent of these potential confounders.

METHODS

We included 202 OA participants with DM and 2,279 without DM from the Osteoarthritis Initiative. Knee pain was evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and a numeric rating scale (NRS). Physical and mental status were assessed by the Medical Outcomes Study Short Form 12 (SF-12) questionnaire, physical component summary (PCS) score and mental component summary (MCS) score, and by the Center for Epidemiologic Studies Depression Scale (CES-D). Linear regression models assessed the influence of DM, adjusted for age, sex, body mass index (BMI), and radiographic severity.

RESULTS

OA participants with DM reported worse knee pain and greater physical and mental issues compared with participants without DM. Individuals with DM had worse KOOS pain (β = -4.72 [95% confidence interval (95% CI) -7.22, -2.23]) and worse NRS pain (β = 0.42 [95% CI 0.04, 0.80]) independent of BMI, OA severity, age, and sex. The negative influence of DM was also apparent for SF-12 PCS (β = -3.49 [95% CI -4.73, -2.25]), SF-12 MCS (β = -1.42 [95% CI -2.57, -0.26]), and CES-D (β = 1.08 [95% CI 0.08, 2.08]).

CONCLUSION

Individuals with knee OA experience on average higher pain intensity and a worse physical and mental health status if they have DM. Linear regression models show that DM is a risk factor for higher pain, in addition to and independent of greater BMI and radiographic OA severity.

[Pain prevention in the primary care setting : Facts for resident physicians]

Based on health insurance data, approximately 37.4 million patients (46%) in Germany are diagnosed with "pain". The prevalence of patients with debilitating chronic pain is around 7.3%. From the health care perspective, and given the high socioeconomic relevance of chronic pain, effective preventive measures represent useful therapeutic approaches. In the context of pain medicine, primary prevention aims to avoid acute pain. Secondary prevention is targeted at preventing acute pain from turning into chronic pain. Tertiary prevention comprises measures to diminish pain-associated disability and impairment to everyday life. Finally, quaternary prevention focuses on avoiding medically non-indicated or unhelpful medical interventions. In addition to general approaches of pain prevention, such as detecting and treating of chronification factors (yellow, black and blue flags), the present article also describes educational and disease-specific approaches in musculoskeletal and neuropathic pain syndromes as well as headaches.

Physiologie der Schmerzentstehung in der Peripherie

Dieser Beitrag gibt einen Überblick über den Kenntnisstand zu den Mechanismen der Schmerzentstehung im Gelenk. Er fokussiert sich auf den Vorgang der Nozizeption in nozizeptiven Nervenfasern des Gelenks und stellt dar, wie Krankheitsprozesse im Gelenk auf Nozizeptoren wirken. Während Nozizeptoren im normalen Gelenk eine hohe Erregungsschwelle besitzen und nur durch hochintensive Reize aktiviert werden, kommt es bei Gelenkerkrankungen häufig zu einer Sensibilisierung dieser Nervenfasern, sodass sie bereits auf leichte Reize (Bewegungen, Palpation) ansprechen und nach zentraler Verarbeitung Schmerzempfindungen auslösen. Eine Sensibilisierung wird meistens durch Entzündungsmediatoren ausgelöst, für die die Nozizeptoren Rezeptoren besitzen. Werden Nervenfasern im Erkrankungsprozess geschädigt, können neuropathische Schmerzmechanismen hinzukommen. Chronische Gelenkerkrankungen sind durch entzündliche und destruktive Prozesse charakterisiert. Sowohl bei primären Arthritiden als auch bei Arthrosen sind entzündliche Prozesse für die Sensibilisierung der Nozizeptoren verantwortlich. Dafür werden neben den Prostaglandinen auch proinflammatorische Zytokine und der Nervenwachstumsfaktor (NGF) verantwortlich gemacht, für die viele Nozizeptoren Rezeptoren exprimieren. Demgemäß sind diese Moleküle auch Target innovativer Schmerztherapien, z. B. die Gabe von Antikörpern gegen NGF bei Arthrose. Besonders für die Neutralisation von TNF ist ein direkt schmerzlindernder Effekt nachgewiesen, der aus der Unterbrechung von nozizeptiven Vorgängen am Nozizeptor resultiert. Der direkte pronozizeptive Effekt der Zytokine und Bindungsstellen für Fc-Fragmente von Antikörpern an Nozizeptoren zeigen, dass Immunmechanismen auch für die Schmerzentstehung große Bedeutung haben. Auch destruktive Gelenkprozesse können Schmerzen verursachen. So kann bereits die Osteoklastenaktivität im präklinischen Stadium einer Arthritis Schmerzen verursachen, und nach Ausbruch der Arthritis tragen Destruktionsprozesse zu Schmerzen bei. Inwieweit die Hemmung der Osteoklastenaktivität Gelenkschmerzen lindert, wird derzeit erforscht. Auch weitere neue Ansätze, peripher wirksame Opioide, Cannabinoide und Ionenkanalblocker werden dargestellt. Schließlich geht der Beitrag auf generelle/systemische Faktoren ein, die Krankheitsprozesse im Gelenk und die Schmerzentstehung beeinflussen. Hier wird in erster Linie die Bedeutung des Diabetes mellitus angesprochen. Diese Stoffwechselerkrankung stellt einen Risikofaktor für die Entwicklung von Arthrosen dar, und sie trägt zur Schmerzintensivierung bei. Dabei können verstärkte Entzündungsprozesse und auch neuropathische Schmerzkomponenten beteiligt sein.

Nerve growth factor antibody for the treatment of osteoarthritis pain and chronic low-back pain: mechanism of action in the context of efficacy and safety

Chronic pain continues to be a significant global burden despite the availability of a variety of nonpharmacologic and pharmacologic treatment options. Thus, there is a need for new analgesics with novel mechanisms of action. In this regard, antibodies directed against nerve growth factor (NGF-Abs) are a new class of agents in development for the treatment of chronic pain conditions such as osteoarthritis and chronic low-back pain. This comprehensive narrative review summarizes evidence supporting pronociceptive functions for NGF that include contributing to peripheral and central sensitization through tropomyosin receptor kinase A activation and stimulation of local neuronal sprouting. The potential role of NGF in osteoarthritis and chronic low-back pain signaling is also examined to provide a mechanistic basis for the observed efficacy of NGF-Abs in clinical trials of these particular pain states. Finally, the safety profile of NGF-Abs in terms of common adverse events, joint safety, and nerve structure/function is discussed.

The Association of Diabetes With Knee Pain Locations, Pain While Walking, and Walking Speed: Data From the Osteoarthritis Initiative

OBJECTIVE

Osteoarthritis (OA) and diabetes mellitus (DM) often coexist and can result in negative outcomes. DM can affect pain and walking speed in people with knee OA; however, the impact of DM on OA is understudied. The purpose of this study was to investigate the association between diabetes and knee pain locations, pain severity while walking, and walking speed in people with knee OA.

METHODS

A cross-sectional analysis was used. Data from 1790 individuals from the Osteoarthritis Initiative (mean [SD] age = 69 [8.7] years) with knee pain were included and grouped into knee OA and diabetes (n = 236) or knee OA only (n = 1554). Knee pain locations were categorized as no pain, localized pain, regional pain, or diffuse pain. Knee pain during a 20-m walk test was categorized as no pain, mild, moderate, or severe knee pain. Walking speed was measured using the 20-m walk test. Multinomial and linear regression analyses were performed.

RESULTS

Diabetes was associated with regional knee pain (odds ratio [OR] = 1.77; 95% CI = 1.01-3.11). Diabetes was associated only with moderate (OR = 1.78; 95% CI = 1.02-3.10) or severe (OR = 2.52; 95% CI = 1.01-6.28) pain while walking. Diabetes was associated with decreased walking speed (B = -0.064; 95% CI = -0.09 to -0.03).

CONCLUSIONS

Diabetes was associated with regional knee pain but not with localized or diffuse knee pain and was associated with moderate to severe knee pain while walking and slower walking speed in people with knee OA.

IMPACT

Clinicians can use a knee pain map for examining knee pain locations for people with diabetes and knee OA. Knee pain during walking and walking speed should be screened for people with knee OA and diabetes because of the influence of diabetes on these parameters in this population.

LAY SUMMARY

Diabetes might be associated with specific knee pain locations, pain during activities such as walking, and reduced walking speed in people with knee OA.

Association of Visceral Adiposity With Pain but Not Structural Osteoarthritis

OBJECTIVE

Osteoarthritis (OA) and pain are both made more severe by low-grade inflammation. This study was undertaken to examine whether visceral fat, a major source of inflammatory cytokines and adipokines, is associated with an increased risk of knee OA or musculoskeletal pain.

METHODS

Subjects in the Multicenter Osteoarthritis Study cohort, who were age 50-79 years and had or were at high risk of knee OA, underwent whole-body dual x-ray absorptiometry (DXA) at baseline. At baseline, 30 months, and 60 months radiographs and magnetic resonance images (MRIs) of the knees were obtained, and patients were asked to score the severity of their knee pain and to identify sites of joint pain using a body homunculus. Baseline DXA scans were used to measure total body fat and visceral and subcutaneous fat in the torso. The association of fat depot size with structural outcomes (incident radiographic OA and cartilage loss and synovitis on MRI) and with pain outcomes (worsening knee pain, number of painful joints, and widespread pain) was assessed. Regression analyses were adjusted for age, sex, race, education level, smoking status, physical activity, body mass index (BMI), and depressive symptoms.

RESULTS

Of the 2,961 participants at baseline, 60.7% were women. The mean age was 62.5 years and mean BMI was 30.5 kg/m2 . After adjustment for covariates, no fat measures were associated with any structural outcomes. However, total and visceral, but not subcutaneous, fat were positively associated with worsening knee pain (P = 0.0005 for total fat and P = 0.007 for visceral fat) and widespread pain (P = 0.001 for total fat and P = 0.02 for visceral fat), and the amount of visceral fat was associated with the number of painful joints (P = 0.07).

CONCLUSION

Our findings indicate that visceral fat is associated with an increased risk of musculoskeletal and widespread pain.

Reductions of cardiovascular and metabolic risk factors after a 14-week periodized training model in patients with knee osteoarthritis: a randomized controlled trial

INTRODUCTION/OBJECTIVE

To evaluate the effects of a periodized circuit training (CT) compared with a conventional strength training (ST) and an educational protocol (EP) on body composition, metabolic parameters, muscle strength, pain, and physical performance in patients with knee osteoarthritis (KOA).

METHOD

This study followed a randomized controlled trial design. A sample of sixty-one patients with KOA, 40-65 years old and BMI < 30 kg/m², were randomly divided into three 14-week protocols: CT, ST, or EP. The CT performed whole body exercises organized in circuit, 3 times a week. The ST performed conventional resistance exercises also 3 times a week, and the EP joined in educational meetings twice a month. Body composition (dual-energy X-ray absorptiometry (DXA)); metabolic parameters (abdominal obesity, triglyceride, HDL, blood pressure and fasting glucose), knee maximal isometric voluntary contraction (MIVC) extension and flexion, performance-based tests (40-m walk test, 30-s chair test, and stair climb test), self-reported pain, stiffness, and physical function (WOMAC) and pain catastrophism were evaluated at baseline and follow-up. Repeated measures ANOVA were used to compare differences between groups (CTxSTxEP) at the different times of assessment (baseline × follow-up). When group-time interaction was found, a one-way ANOVA, followed by a Bonferroni post hoc test, was used to compare groups in each time point; while a paired t test was used to verify the time effect in each group. Additionally, the training effect was analyzed in terms of the percent change (Δ%). Effect size was calculated for post intervention (week 14) between groups. For all analyses a significance level of 5% was adopted (p < 0.05).

RESULTS

The CT was the only protocol that presented significant lower body mass (p = 0.018; Δ% = - 1.4), fat mass (p = 0.017; Δ% = - 10.3), %fat mass (p < 0.001; Δ% = - 13.9), adipose indices (%fat trunk/%fat legs p = 0.031; Δ% = 7.8; fat mass/height² p = 0.011; Δ% = - 15.1; trunk/limb fat mass p = 0.012; Δ% = - 8.2; visceral adipose tissue (VAT) volume (cm³) p = 0.039; Δ% = - 11.6; VAT area (cm²) p = 0.044; Δ% = - 12.2), blood pressure levels (SBP p = 0.042; Δ% = - 3.4 and DBP p = 0.001; Δ% = - 4.9), higher lean mass and HDL (p < 0.001; Δ% = 5.9) compared to baseline. CT and ST presented lower WOMAC pain, stiffness and physical function (p < 0.001; Δ% = - 64.0 for CT and p < 0.001; Δ% = 0.001; Δ% = - 46.4 for ST in WOMAC total score, pain catastrophizing (p < 0.001; Δ% = - 66.7 for CT and p < 0.001; Δ% = - 61.5 for ST) a higher functional performance (30 s chair test: p < 0.001; Δ% = 45.7 for CT and p < 0.001; Δ% = 26.9 for ST; 40 m walk test: p < 0.001; Δ% = 26.7 for CT and p < 0.001; Δ% = 12.5 for ST; stair climb test: p = 0.002; Δ% = - 33.9 for CT and p < 0.001; Δ% = - 18.8 for ST) and knee extension MIVC (p < 0.001; Δ% = 21.92 for CT and p < 0.001; Δ% = 30.25 for ST).

CONCLUSION

A periodized CT model reduces visceral adipose tissue, SBP and DBP, and improves HDL, important cardiovascular and metabolic risk factors, in patients with KOA. Both trained groups (CT and ST) improve self-reported clinical symptoms, muscle strength, and physical performance in this sample.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov , NCT02761590 (registered on May 4, 2016).

KEY POINTS

• A 14-week periodized circuit training reduces visceral adipose tissue, systolic and diastolic blood pressure, and improves HDL blood levels in patients with knee osteoarthritis. • Both periodized circuit training and conventional strength training improve clinical symptoms, functional performance and muscle strength in this sample.

The Association of Diabetes with Knee Pain Severity and Distribution in People with Knee Osteoarthritis using Data from the Osteoarthritis Initiative

Limited research has examined the association between diabetes mellitus (DM) and knee pain in people with osteoarthritis (OA). Therefore, this study aimed at examining the association between DM and knee pain severity, and to explore the association between DM and knee pain distribution (unilateral or bilateral versus no pain) in subjects with knee OA. This is a cross-sectional analysis of the baseline visit of individuals who were enrolled in the Osteoarthritis Initiative. Data of participants with knee OA were used for this analysis (n = 1319), and grouped into subjects with both knee OA and DM (n = 148) or knee OA only without DM (n = 1171). Pain severity was measured using a numeric rating scale from 0 to 10 over the past 7 and 30 days for each knee, and the more symptomatic knee with higher pain severity was chosen for analysis. DM was significantly associated with increased knee pain severity over 7 days (B 0.68; 95% CI 0.25-1.11) and over 30 days (B 0.59; 95% CI 0.17-1.01) after adjustments for all covariates, including age, gender, BMI, race, depression symptoms, composite OA score, use of pain medications, and knee injections. Multinomial regression showed that participants with knee OA and DM had 2.45 (95% CI 1.07-5.61) to 2.55 (95% CI 1.12-5.79) times higher likelihood of having unilateral and bilateral knee pain than those without DM and without knee pain. This study found that DM was associated with higher pain severity and unilateral and bilateral knee pain distribution.

Association of diabetes mellitus with postoperative opioid consumption in patients undergoing primary unilateral hip arthroplasty

Opioids are an indispensable component of perioperative pain management; however, the burgeoning opioid epidemic necessitates research into the risk factors for the development of opioid dependence and abuse following surgery. Diabetes has been identified as a risk factor for prolonged opioid utilisation following non-orthopaedic surgery; however, this association has not been investigated following orthopaedic surgery. To bridge this gap in the literature, we performed a retrospective propensity-matched cohort study in patients undergoing primary unilateral total hip arthroplasty. Propensity-matched cohorts were created to compare patients with and without preexisting diabetes mellitus. Outcomes of interest were opioid utilisation and subjective pain on postoperative day 1. Our results did not identify an association between preexisting diabetes and postoperative pain or opioid utilisation. While this study did not identify an association between diabetes and opioid utilisation following total hip arthroplasty, future studies should pursue a prospective, longitudinal approach and investigate other common orthopaedic procedures.

Topical application of Chinese herbal medicine DAEP relieves the osteoarthritic knee pain in rats

Background

The potential adverse effects of conventional oral pharmacotherapy of osteoarthritis (OA) restrict their long-term use. Topical application of a Chinese herbal paste for relieving OA knee pain can be effective and safe. However, evidence-based scientific research is insufficient to support its application worldwide. The aim of this study was to investigate the in vivo efficacy of a topical Chinese herbal paste on relieving OA knee pain and its underlying mechanism.

Methods

An OA rat model was developed by anterior cruciate ligament transection (ACLT) followed by treadmill running. A herbal paste including Dipsaci Radix, Achyranthis Bidentatae Radix, Eucommiae Cortex and Psoraleae Fructus, named as DAEP, was applied topically on the knee joint of the rats (DAEP). The rats without DAEP treatment served as Control. Rats with surgery but without ACLT, treadmill running and DAEP treatment acted as Sham. The morphologic change of the knee joint was observed radiographically. Nociception from the knee of the rats was assessed using Incapacitent test and CatWalk gait system. The therapeutic mechanism was investigated by analyzing the gene and protein expression of inflammatory markers via qPCR and Western blot, respectively.

Results

Radiographic images showed less destruction at the posterior tibial plateau of the DAEP group compared with the Control after 2 weeks of treatment. The static weight ratio and the gait parameters of the Control were reduced significantly via Incapacitance test and CatWalk gait analysis, respectively. DAEP treatment increased the Print Area and Maximum Intensity significantly compared with the Control. DAEP significantly suppressed the upregulation of gene expression of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and inducible nitric oxide synthase (iNOS).

Conclusions

DAEP exhibited its effect via the nuclear factor (NF)-κB pathway by suppressing the phosphorylation of IκB kinase αβ (p-IKKαβ) and cyclooxygenase-2 (COX-2) protein expression. This study provides scientific evidence to support the clinical application of the Chinese herbal paste on reliving OA pain.

Less Severe Preoperative Synovitis is Associated With Higher Self-reported Pain Intensity 12 Months After Total Knee Arthroplasty-An Exploratory Prospective Observational Study

OBJECTIVES

Synovitis is one of the possible pain generators in osteoarthritis (OA) and is associated with upregulation of proinflammatory cytokines, which can lead to worsening of the postoperative pain. This exploratory study aimed to investigate the association between perioperative synovitis and self-reported pain 12 months after total knee arthroplasty (TKA) in patients with OA.

MATERIALS AND METHODS

Twenty-six knee OA patients were included in this analysis. The perioperative volume of synovitis in predefined locations was assessed by contrast-enhanced magnetic resonance imaging (CE-MRI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Perioperative synovitis was assessed histologically from biopsies of the synovium. Highest pain intensity within the last 24 hours (Visual Analog Scale, VAS, 0 to 100) was assessed before and 12 months after TKA. Patients were divided into a low-pain intensity (VAS≤30) and a high-pain intensity (VAS>30) group on the basis of 12 months postoperative VAS.

RESULTS

The high-pain intensity group had significantly lower perioperative contrast-enhanced-synovitis (P=0.025), DCE-synovitis (P<0.04), and a trend toward lower histologically assessed synovitis (P=0.077) compared with the low-pain intensity group. Perioperative synovitis scores were inversely correlated with pain intensity 12 months after TKA (P<0.05), indicating that more severe perioperative synovitis is associated with less severe pain intensity at 12 months.

DISCUSSION

Higher degrees of perioperative synovitis scores are found to be associated with less postoperative pain 12 months after TKA. Further, correlation analysis revealed that less severe perioperative CE-MRI and DCE-MRI synovitis was associated with higher pain intensity 12 months after TKA, suggesting that CE-MRI and DCE-MRI synovitis grades could be used as imaging markers for prediction of chronic postoperative pain after TKA.

Transient Receptor Potential vanilloid 4 ion channel in C-fibres is involved in mechanonociception of the normal and inflamed joint

The Transient Receptor Potential vanilloid 4 ion channel (TRPV4) is an important sensor for osmotic and mechanical stimuli in the musculoskeletal system, and it is also involved in processes of nociception. In this study we investigated the putative role of TRPV4 ion channels in joint pain. In anesthetized rats we recorded from mechanosensitive nociceptive A∂- and C-fibres supplying the medial aspect of the knee joint. The intraarticular injection of the TRPV4 antagonist RN-1734 into the knee joint reduced the responses of C-fibres of the normal joint to noxious mechanical stimulation and the responses of the sensitized C-fibres of the acutely inflamed joint to innocuous and noxious mechanical stimulation. The responses of nociceptive A∂-fibres were not significantly altered by RN-1734. The intraarticular application of the TRPV4 agonists 4αPDD, GSK 1016790 A, and RN-1747 did not consistently alter the responses of A∂- and C-fibres to mechanical stimulation of the joint nor did they induce ongoing activity. We conclude that TRPV4 ion channels are involved in the responses of C-fibres to noxious mechanical stimulation of the normal joint, and in the enhanced sensitivity of C-fibres to mechanical stimulation of the joint during inflammation of the joint.

The Prevalence of Osteoarthritis and Risk Factors in the Korean Population: The Sixth Korea National Health and Nutrition Examination Survey (VI-1, 2013)

Background

Knee osteoarthritis is highly prevalent, especially among the elderly. However, its risk factors have not been well identified, especially in the Korean population. This study aimed to assess the epidemiologic characteristics and risk factors of knee osteoarthritis in the Korean population.

Methods

Data of 2,280 (1,295 women) participants of the 2013 Korea National Health and Nutrition Examination Survey aged ≥50 years who underwent knee radiography were analyzed. According to the American College of Rheumatology clinical/radiographic classification criteria, knee osteoarthritis was defined as knee pain and radiographic knee osteoarthritis. The association between risk factors and knee osteoarthritis was analyzed using the chi-square test and binominal logistic regression.

Results

The participants had an average age of 62.6 years; 56.8% of them were women. The average body mass index was 24.2 kg/m², and 296 (13%) participants were diagnosed with knee osteoarthritis. After adjustment for multiple risk factors, age of ≥65 years (adjusted odds ratio [OR], 2.552; 95% confidence interval [CI], 1.868–3.486), female sex (OR, 2.050; 95% CI, 1.275–3.295), obesity (body mass index, ≥25.0 kg/m² ; OR, 1.563; 95% CI, 1.191–2.051), hypertension (OR, 1.394; 95% CI, 1.052–1.846), low educational level (lower than or equal to elementary school: OR, 4.761; 95% CI, 2.131–10.635; middle school: OR, 3.184; 95% CI, 1.375–7.369), and low strength exercise frequency (<2 times/wk; OR, 1.829; 95% CI, 1.202–2.784) increased the risk of knee osteoarthritis.

Conclusion

Old age, sex, obesity, hypertension, low educational level, and low strength exercise frequency were found to be risk factors for knee osteoarthritis.