Exploring Anatomo-Morphometric Characteristics of Infrapatellar, Suprapatellar Fat Pad, and Knee Ligaments in Osteoarthritis Compared to Post-Traumatic Lesions

Mechanical insights into fat pads: a comparative study of infrapatellar and suprapatellar fat pads in osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is the most common musculoskeletal disorder, primarily affecting knee joints and causing pain and disability. The infrapatellar (IFP) and the suprapatellar (SFP) fat pad are knee adipose tissues that play essential mechanical roles during articular activity but are also sources of adipokines and cytokines, contributing to OA progression. For this reason, this work aims to provide new insights into IFP and SFP implications in knee OA.

MATERIALS AND METHODS

IFP and SFP tissue mechanical properties were studied through compression, indentation and shear mechanical tests performed on samples collected from patients who underwent total knee arthroplasty surgery due to end-stage OA. The energy loss, peak stress, and initial and final elastic moduli were calculated from the unconfined compression tests. The time-dependent response, evaluated in terms of equilibrium relative stiffness, was computed from stress-relaxation loading conditions. Considering shear tests, they provided strain-energy dissipation density, peak shear stress, and the shear moduli.

RESULTS

Experimental results showed the typical adipose tissue mechanics features: non-linear stiffening with strain and time-dependent response. Experimental results showed that OA IFP is stiffer than OA SFP, indeed IFP final compression elastic modulus was greater than the SFP (84.43 kPa vs 35.54 kPa respectively) (p = 0.042). Regarding the viscoelastic properties they were comparable: the equilibrium relative stiffness was reported as 0.13 for IFP and 0.11 for SFP (p = 0.026).

CONCLUSIONS

These outcomes provide new insights into the OA influence on knee mechanics and lay the basis for developing computational tools to improve knee prosthesis design.

Human umbilical cord mesenchymal stem cell-derived exosomal miR-199a-3p inhibits the MAPK4/NF-κB signaling pathway to relieve osteoarthritis

BACKGROUND

There is currently no effective treatment for osteoarthritis (OA), which is the most common joint disorder leading to disability. Although human umbilical cord mesenchymal stem cells (hUC-MSCs) are promising OA treatments, their use is limited by the condition itself, and understanding of the underlying mechanisms of OA is lacking.

AIM

To explore the specific molecular mechanism by which hUC-MSC-derived exosomal miR-199a-3p improves OA.

METHODS

Sodium iodoacetate was injected into rat articulations to construct an animal model of OA. Interleukin (IL)-1β was used to induce human chondrocytes (CHON-001) to construct an OA chondrocyte model. Exosomes in hUC-MSCs were isolated using Ribo™ Exosome Isolation Reagent. Real-time reverse transcriptase-polymerase chain reaction and western blotting were used to detect the expression of related genes and proteins, and damage to CHON-001 cells and rat articular cartilage tissue was evaluated by enzyme-linked immunosorbent assay, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-nick end labelling staining and hematoxylin and eosin staining.

RESULTS

hUC-MSC-derived exosomes (hUC-MSC-Exos) inhibited the expression of IL-1β-induced inflammatory cytokines, namely, IL-6, IL-8 and tumor necrosis factor-α. hUC-MSC-Exos also improved the viability but inhibited the apoptosis of CHON-001 cells, improved the pathological condition of articular cartilage tissue and alleviated the development of OA in vivo. Mechanistically, hUC-MSC-Exos downregulated the expression of mitogen-activated protein kinase 4 by delivering miR-199a-3p, thereby inhibiting the activation of the nuclear factor-kappaB signaling pathway, alleviating IL-1β-induced chondrocyte inflammation and apoptosis, and ultimately improving the development of OA.

CONCLUSION

hUC-MSC-derived exosomal miR-199a-3p alleviates OA by inhibiting the mitogen-activated protein kinase 4/nuclear factor-kappaB signaling pathway. The present findings suggest that miR-199a-3p delivery by hUC-MSC-Exos may be a novel strategy for the treatment of OA.

Infrapatellar fat pad as a source of biomarkers and therapeutic target for knee osteoarthritis

BACKGROUND AND OBJECTIVE

Osteoarthritis (OA) is a multifactorial and highly prevalent disease in elderly adults; however, its pathogenesis, diagnosis, and treatment are unmet needs nowadays. Research efforts have focused on elucidating the molecular mechanisms involved in the pathogenesis, onset, and progression of OA to facilitate early detection and effective therapeutic approaches. Infrapatellar fat pad (IPFP) represents a promising novel source of OA biomarkers given that it is an active player in OA. This review aims to investigate the current literature regarding the potential of the IPFP as a source of diagnostic and prognostic biomarkers for OA as well as potential target for novel therapies.

METHODS

A literature search was conducted in the PubMed database in June 2024. We included cross-sectional and longitudinal studies based on IPFP from human OA patients, oriented in the identification of imaging, biochemical, and molecular biomarkers in the IPFP.

RESULTS

After screening and evaluation, we included a total of 61 studies. Most of the imaging publications (n = 47) on IPFP are based on magnetic resonance imaging (MRI) that revealed potential semiquantitative and quantitative imaging biomarkers linked to inflammation, fibrosis, pain, and joint degeneration imaging parameters. Biochemical and molecular studies (n = 14) pointed out an increase in interleukin-6 (IL-6), fatty acid-binding protein 4 (FABP4), adiponectin, and lysophosphatidylcholine (LysoPC) in the IPFP during OA progression.

CONCLUSIONS

Imaging, biochemical, and molecular studies indicate OA potential biomarkers in the IPFP related to inflammation, lipid dysregulation, and fibrosis. The combination of imaging and biochemical biomarkers could provide a better prediction of OA onset and the identification of OA progressors at an early stage. The IPFP study could also reveal potential therapeutic targets with the vision of better precision medicine.

Quantification of infrapatellar fat pad fibrosis using magnetic resonance imaging-derived proton density fat fraction: a pathology-controlled study

Background

Knee osteoarthritis (KOA) is a degenerative joint disease leading to disability in the elderly. Fibrosis of the infrapatellar fat pad (IPFP) impacts knee joint function and disease progression. Accurate assessment of IPFP fibrosis aids early intervention and treatment. The aim of this study was to evaluate the diagnostic efficacy of proton density fat fraction (PDFF) and T2* measurements using mDixon-Quant technology in assessing IPFP fibrosis in KOA.

Methods

A total of 47 patients were included in this study (23 patients without fibrosis, 17 with mild fibrosis, and 7 with severe fibrosis). Knee magnetic resonance (MR) scans were performed on a 3.0 T MR system. MR sequences included 3.0 T, sagittal T2-weighted images, proton density-weighted spectral adiabatic inversion recovery (PDW-SPAIR), and three-dimensional (3D) six-echo gradient recalled echo sequence (mDixon-Quant). Two radiologists performed PDFF, T2* measurements, and the hypointense signal grade of the IPFP. Measurements were compared among the three subgroups, and correlations of the three parameters with pathology-derived IPFP fibrosis degree and diagnostic efficacy were evaluated. Intraclass correlation coefficient (ICC), one-way analysis of variance (ANOVA), and Spearman correlation analysis were used. The diagnostic performance was assessed using the area under the receiver operating characteristic (ROC) curve (AUC) and linear regression with leave-one-out cross validation. Statistical significance was set at P<0.05.

Results

MR measurements demonstrated good inter-observer reproducibility (ICC for PDFF =0.901, ICC for T2* =0.902). The PDFF and T2* values in the normal and mild fibrosis groups were higher than those in the severe fibrosis group. PDFF and T2* measurements were strongly correlated with IPFP fibrosis (ρ=-0.7083, -0.6028, respectively). PDFF and T2* showed good diagnostic performance for IPFP fibrosis (AUC =0.9529, 0.8098, respectively). Adjusted R2 indicated similar results (PDFF 0.6682, T2* 0.538, hypointense 0.1437). Using PDFF and T2* together showed good diagnostic performance for IPFP fibrosis (AUC =0.9601) and had the best R2 of 0.6995.

Conclusions

PDFF and T2* measurements based on mDixon technology provide a non-invasive and quantitative assessment of IPFP fibrosis, especially PDFF.

Knee Effusion-Synovitis Is Not Associated With Self-Reported Knee Pain in Division I Female Athletes

BACKGROUND

Recent research indicates a potential link between effusion-synovitis and knee pain in athletes. This study investigates the association of knee effusion-synovitis with self-reported knee pain in elite female athletes, leveraging ultrasound imaging for effusion-synovitis assessment.

HYPOTHESIS

Presence of knee effusion-synovitis is associated with increased self-reported knee pain in Division I female athletes.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 53 NCAA Division I female athletes underwent bilateral knee ultrasound to identify effusion-synovitis. The Knee Injury and Osteoarthritis Outcome Survey (KOOS) Pain subscale assessed knee pain. A 1-way analysis of variance compared KOOS pain, symptoms, activities during daily living (ADL), and quality of life (QoL) scores across groups with no, unilateral, and bilateral effusion-synovitis.

RESULTS

Among the athletes, 49.1% showed no effusion-synovitis, 26.4% had unilateral, and 24.5% had bilateral effusion-synovitis. There were no differences in self-reported pain scores (F = 0.027; P = 0.97), ADL (F = 0.256; P = 0.78), or QoL (F = 0.120; P = 0.88) between any groups. In addition, the frequency of effusion-synovitis was as follows: for the right limb, Grade 0 = 35 (66%), Grade 1 = 15 (28%), Grade 2 = 1 (2%), and Grade 3 = 2 (4%); for the left limb, Grade 0 = 31 (58%), Grade 1 = 19 (36%), Grade 2 = 3 (6%), and Grade 3 = 0 (0%).

CONCLUSION

The presence of effusion-synovitis, irrespective of being unilateral or bilateral, was not associated with self-reported knee pain in elite female athletes. This suggests that lower grades of effusion-synovitis may not significantly impact knee pain.

CLINICAL RELEVANCE

The findings of this study challenge existing assumptions about the impact of effusion-synovitis on knee pain in athletes, contributing to the nuanced understanding of knee joint health in sports medicine.

Influence of infrapatellar fat pad size on the development and severity of chondromalacia patella

The inflammatory role of the infrapatellar fat pad (IPFP) in cartilage damage has been well-documented, yet its potential protective function as a shock absorber remains underexplored. This retrospective cohort study aimed to evaluate the relationship between the IPFP size and chondromalacia patella (CP), while also examining the effects of age, sex, and body mass index (BMI). Magnetic resonance imaging scans from 311 patients aged 40 to 65 years were retrospectively analyzed. Axial sequences classified CP severity, and sagittal sequences measured IPFP areas. CP was graded according to the International Cartilage Repair Society system, and patients were grouped into control (no CP), mild CP (grades 1-2), and severe CP (grades 3-4) categories. Demographic data, including age, sex, and BMI, were collected, and statistical analysis explored the relationships between IPFP area, CP severity, and these factors. Of the patients, 145 (46.6%) had no CP, while 166 (53.4%) had varying CP severity. Patients with CP had significantly smaller IPFP areas (6.16 ± 0.67 cm2) compared to controls (6.96 ± 0.87 cm2, P < .001). The mean IPFP area decreased progressively with increasing CP severity. After adjusting for confounders, a smaller IPFP area was significantly associated with the presence and severity of CP (P < .001). These findings provide evidence that a larger IPFP area plays a protective role in maintaining patellar cartilage integrity and mitigating CP progression, as demonstrated by a significant inverse correlation between IPFP area and CP severity, independent of age, sex, and BMI. A comprehensive, multidisciplinary approach integrating biomechanical, metabolic, and inflammatory factors is warranted to fully elucidate the role of IPFP in CP.

Quantitative MRI reveals infrapatellar fat pad changes after running a marathon

Background

Marathon running, while offering health benefits, is associated with a high incidence of knee injuries. The infrapatellar fat pad (IFP) plays a critical role in knee joint homeostasis and injury mitigation. This study investigated IFP adaptations to the acute stress of marathon running using quantitative magnetic resonance imaging (MRI).

Methods

Fourteen amateur marathon runners (12 male, two female) were prospectively enrolled and underwent 3.0T MRI (GE SIGNA Architect) one week before and after the marathon. Left knee imaging included MAGiC and IDEAL-IQ sequences. MAGiC sequences provide T1, T2, and proton density (PD) maps. IDEAL-IQ sequences yield fat fraction (FF), representing the relative amount of fat within the IFP, and the transverse relaxation rate (R2*) within the IFP. IFP volume and maximum cross-sectional area were quantified. Two experienced radiologists independently analyzed the images using dedicated software. Inter-observer reliability for quantitative MRI measurements was assessed using intraclass correlation coefficients (ICCs). Paired t-tests were used to compare pre- and post-marathon measurements of T1, T2, FF, R2* values, IFP volume and maximum cross-sectional area. Pearson correlation analysis explored relationships between changes in IFP parameter changes and participant characteristics. P < 0.05 was considered statistically significant for all analyses.

Results

Post-marathon, IFP FF significantly increased (p < 0.05), while IFP volume significantly decreased (p < 0.05), T1 and T2 values showed a decreasing trend. IFP appeared morphologically compressed post-marathon. A significant negative correlation was found between FF change and both body weight and body mass index (BMI) (p < 0.05).

Conclusions

This study provides novel evidence of robust IFP adaptation to marathon running, characterized by increased FF and potential fluid shifts, suggesting enhanced cushioning and load dissipation. These findings highlight the importance of considering individual biomechanics in understanding IFP function and injury susceptibility. Future research should clarify the clinical implications of these adaptations for runner injury prevention and rehabilitation.

Body roundness index and the risk of knee osteoarthritis: evidence from the China Health and Retirement Longitudinal Study

Objective

Previous cross-sectional studies have demonstrated that the body roundness index (BRI) is associated with knee osteoarthritis (KOA). However, no longitudinal studies have confirmed this association. This study aims to explore the link between BRI and KOA risk in the Chinese population through longitudinal analysis and to evaluate its utility in early diagnosis and risk prediction.

Methods

This study utilizes data from the China Health and Retirement Longitudinal Study (CHARLS). A total of 7,318 participants who were followed from 2015 to 2020 were included. BRI was calculated using physical examinations and questionnaire data, and participants were categorized by quartiles. The relationship between BRI and KOA risk was assessed using multivariate weighted regression models and trend tests, while subgroup and sensitivity analyses were conducted to ensure the robustness of the findings.

Results

After 5 years of follow-up, 1,035 participants (14.14%) were diagnosed with KOA. Findings indicate a positive correlation between BRI and KOA risk (HR = 1.08, 95% CI: 1.02-1.13, p = 0.0039), with an increasing trend in KOA risk across BRI quartiles (p for trend = 0.0033). Subgroup analysis reveals that the association is particularly strong among individuals aged 50-59, males, those living in rural areas, and those without cardiovascular disease.

Conclusion

This study establishes that an increase in BRI significantly elevates KOA risk. These findings suggest that BRI could be an effective tool for KOA risk assessment and could contribute to the development of personalized prevention strategies. Additionally, BRI is valuable in elucidating the potential mechanisms linking body fat distribution and inflammatory responses in KOA progression.

Danggui niantong decoction attenuates synovial fibrosis through regulating PI3k/AKT signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCY

Danggui Niantong Decoction (DGNTD) is a traditional Chinese medicine compound formula that has been demonstrated to possess efficacy in the treatment of rheumatoid arthritis (RA) and osteoarthritis (OA), as well as for dispelling moisture and relieving pain. As mentioned before, DGNTD is essential for synovial inflammation in RA. The primary features of the OA synovial membrane are low-grade inflammation, hyperplasia with enhanced fibroblast-like synoviocytes (FLS) proliferation, and fibrosis, which can cause pain and stiffness. However, it is still unknown how DGNTD functions in the OA synovium.

AIM OF THE STUDY

Clarify the influence of DGNTD on OA synovium and investigate potential mechanisms of action.

METHODS AND MATERIALS

The principal constituents of DGNTD were detected using liquid chromatography-mass spectrometry (LC-MS) analysis. To evaluate the effect of DGNTD on synovial inflammation and fibrosis, a transforming growth factor beta (TGF-β)-stimulated rat FLS cell model and a rat OA animal model based on anterior cruciate ligament transection (ACLT) and partial medial meniscectomy (MMx) were employed.

RESULTS

Our results showed that 322 components were detected using LC-MS. In vivo, DGNTD therapy reduced pain, synovial inflammation, and fibrosis. The therapy significantly reduced levels of pain-related molecules, specifically calcitonin gene-related peptide (CGRP) and inducible nitric oxide synthase (iNOS), as well as fibrotic markers, including alpha smooth muscle actin (α-SMA) and type III collagen alpha-1 (Col3a1), in the synovium. A proteomics study demonstrated that DGNTD decreased the fibrotic protein Col3a1. DGNTD reduced the mRNA expression of pro-inflammatory and fibrotic markers (tumor necrosis factor alpha (TNF-α), interleukin-1 beta(IL-1β), interleukin-6(IL-6), α-SMA, Col3a1and TGF-β) in TGF-β-induced FLS. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and validation results revealed that DGNTD inhibits synovial fibrosis via the phosphatidylinositol 3-kinase (PI3K)/protein Kinase B (AKT) signaling pathway.

CONCLUSIONS

DGNTD partially relieves pain, synovitis, and synovial fibrosis by regulating the PI3K/AKT pathway. These findings provide fresh information about the underlying mechanisms and successful therapy of OA, as well as a theoretical and experimental foundation for the clinical management of OA using DGNTD.

B Cell Activation, Differentiation, and Their Potential Molecular Mechanisms in Osteoarthritic Synovial Tissue

Objective

The objective of this study was to characterize the activation and differentiation of B cells in the synovium of osteoarthritis (OA) and to explore the underlying molecular mechanisms.

Methods

Peripheral blood and synovial samples from OA patients at different stages were collected, and flow cytometry was employed to analyze the activation and differentiation of B cells. Immunofluorescence staining of joint synovium from OA mice at different stages was conducted to assess mice joint synovium B cell activation and differentiation. Co-culture experiments of synovial fibroblasts with B cells were performed to investigate the influence of synovial cells on B cell activation and differentiation. Finally, transcriptome analysis was utilized to identify potential key molecules and pathways.

Results

In OA patients, the infiltration, activation, and differentiation of B cells in synovium and peripheral blood exhibited distinct characteristics. Specifically, the proportion of activated CD86+ B cells and the differentiation marker HLA-DR+ increased with disease severity, whereas the proportion of the differentiation marker IgM decreased. The proportion of CD38+ B cells also decreased with increasing severity, although this change lacked statistical significance. Immunofluorescence staining of CD19+ and CD86+ cells in mice indicated increased expression with greater OA severity. Co-culture experiments demonstrated that OA synovial fibroblasts promoted B cell activation and differentiation, as evidenced by higher expression levels of CD86+ and HLA-DR+ in the OA group compared to controls. Additionally, the proportion of naive B cells decreased as disease severity progressed.

Conclusion

Synovial fibroblasts in OA have been shown to promote the differentiation and activation of B cells, indicating that B cells play a significant role in the pathogenesis of synovium inflammation in OA.

Novel insights into the role of metabolic disorder in osteoarthritis

Osteoarthritis (OA) is a prevalent condition that affects individuals worldwide and is one of the leading causes of disability. Nevertheless, the underlying pathological mechanisms of OA remain inadequately understood. Current treatments for OA include non-drug therapies, pharmacological interventions, and surgical procedures. These treatments are mainly focused on alleviating clinical manifestations and improving patients' quality of life, but are not effective in limiting the progression of OA. The detailed understanding of the pathogenesis of OA is extremely significant for the development of OA treatment. Metabolic syndrome has become a great challenge for medicine and public health, In recent years, several studies have demonstrated that the metabolic syndrome and its individual components play a crucial role in OA. Consequently, this review summarizes the mechanisms and research progress on how metabolic syndrome and its components affect OA. The aim is to gain a deeper understanding of the pathogenesis of OA and explore effective treatment strategies.

Innovative Approaches in Knee Osteoarthritis Treatment: A Comprehensive Review of Bone Marrow-Derived Products

Knee osteoarthritis (OA) is a chronic articular disease characterized by the progressive degeneration of cartilage and bone tissue, leading to the appearance of subchondral cysts, osteophyte formation, and synovial inflammation. Conventional treatments consist of non-steroidal anti-inflammatory drugs (NSAIDs), analgesics, and glucocorticoids. However, the prolonged use of these drugs causes adverse effects. NSAIDs, for instance, are known to be nephrotoxic, increasing the damage to articular cartilage. New therapies capable of accelerating the process of tissue regeneration and repair are being discussed, such as the use of orthobiologics that are naturally found in the body and obtained through minimally invasive collection and/or laboratory manipulations. Bone marrow aspirate (BMA) and bone marrow aspirate concentrate (BMAC) are both rich in hematopoietic stem cells, mesenchymal stem cells (MSCs), and growth factors (GFs) that can be used in the healing process due to their anabolic and anti-inflammatory effects. The aim of this literature review is to assess the efficacy of BMA and BMAC in the treatment of knee OA based on the favorable results that researchers have obtained with the use of both orthobiologics envisaging an accelerated healing process and the prevention of OA progression.

α-klotho reduces susceptibility to osteoarthritis: evidence from cross-sectional studies and Mendelian randomization

Background

Despite extensive research, the association between serum α-klotho levels and osteoarthritis (OA) remains unclear, predominantly relying on findings from OA mouse models. This study used data from the National Health and Nutrition Examination Survey (NHANES) to conduct a cross-sectional study examining the relationship between α-klotho and human OA. In addition, we used Mendelian randomization (MR) to genetically infer a causal relationship between serum α-klotho and the three OA subtypes.

Method

A cohort of 12,037 subjects from NHANES (2007-2016) was analyzed. Multivariate logistic regression was utilized to examine the association between α-klotho concentration and OA, alongside subgroup analysis and interaction tests. Additionally, a two-sample bi-directional MR analysis was conducted to evaluate the relationship between serum α-klotho and three OA subtypes, including all OA, hip OA, and knee OA, employing the inverse variance weighting (IVW) method as the primary approach.

Results

Following adjustment for covariates, a nonlinear negative correlation between serum α-klotho and OA was observed (OR=0.77; 95% CI, 0.68-0.88, p < 0.0001). The IVW method revealed that higher serum α-klotho levels were associated with decreased susceptibility to hip OA (OR = 0.92, 95% CI: 0.87-0.98, P = 9.64×10-3). However, MR analysis did not establish a causal relationship between serum α-klotho and OA or knee OA. Inverse MR also indicated that the three subtypes of OA do not causally affect serum α-klotho concentrations.

Conclusions

In cross-sectional studies, α-klotho showed a nonlinear negative correlation with OA. MR analysis of outcomes was not identical to cross-sectional studies.

The biphasic role of the infrapatellar fat pad in osteoarthritis

Osteoarthritis (OA) is a progressive degenerative disease resulting in joint deterioration. It is a whole organ disease characterized by cartilage degeneration and varying degrees of synovitis, involving pathological changes in all joint tissues, such as cartilage, subchondral bone, ligaments, meniscus, synovium, and infrapatellar fat pad (IPFP). IPFP is the largest adipose tissue structure in the knee joint and is composed of fat cells, immune cells and blood vessels. Moreover, IPFP is located close to the cartilage and bone surface so that it may reduce the impact of loading and absorb forces generated through the knee joint, and may have a protective role in joint health. IPFP has been shown to release various cytokines and adipokines that play pro-inflammatory and pro-catabolic roles in cartilage, promoting OA progression. Intra-articular injections of IPFP-derived mesenchymal stem cells and exosomes have been shown to reduce pain and prevent OA progression in patients with knee OA. Previous studies have shown that IPFP has a biphasic effect on OA progression. This article reviews the latest research progress of IPFP, discusses the role and mechanism of IPFP in OA, provide new intervention strategies for the treatment of OA. This article will also discuss the handling of IPFP during the procedure of total knee arthroplasty.

Current Evidence on and Clinical Implications of Vitamin D Levels in Pain and Functional Management of Knee Osteoarthritis: A Systematic Review

BACKGROUND

Osteoarthritis is a common chronic disease that affects quality of life and increases public health costs. Knee osteoarthritis is a frequent form, marked by joint degeneration, pain, stiffness, and functional restrictions. Factors such as age, genetics, joint injuries, obesity, and vitamin D deficiency can affect knee osteoarthritis progression. While the exact link between vitamin D and osteoarthritis is still being studied, recent research indicates that low vitamin D levels might influence the articular cartilage's structure and function, potentially accelerating osteoarthritis. This review aims to analyze the last decade of research on vitamin D's role in osteoarthritis.

METHODS

A systematic review of the literature was conducted in accordance with the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Relevant studies from the last ten years were included to evaluate the association between vitamin D levels and knee osteoarthritis. The inclusion criteria were studies examining the role of vitamin D in cartilage health and osteoarthritis progression and the potential clinical implications for disease management.

RESULTS

This review identified a variety of studies exploring the connection between vitamin D and osteoarthritis, with mixed findings.

CONCLUSIONS

The relationship between vitamin D and knee osteoarthritis remains inconclusive, highlighting the need for further research. An updated evaluation of the literature is crucial for osteoarthritis management strategies and to potentially include vitamin D supplementation in therapeutic protocols.

Interleukin-37 Inhibits Interleukin-1β-Induced Articular Chondrocyte Apoptosis by Suppressing Reactive Oxygen Species

Objective: Chondrocyte apoptosis has been considered a crucial mechanism that is responsible for cartilage destruction in osteoarthritis (OA). The mechanism of interleukin-37 (IL-37) on chondrocyte apoptosis has not been clearly determined in the pathogenesis of OA. Here, we explored the role of IL-37 in the regulation of cellular apoptosis in rat chondrocytes stimulated by IL-1β. Methods: Rat chondrocytes were used in in vitro study, and were stimulated with IL-1β (10 ng/mL) and/or recombinant IL-37 (rIL-37; 100 ng/mL) after cytotoxicity assessments using these cytokines were conducted. After rIL-37 treatment of chondrocytes stimulated with IL-1β, the cell proliferation assay, apoptosis assays, including expression of mitochondrial apoptosis-related markers, flow cytometry analysis of annexin V-FITC/propidium iodide (PI), cell cycle analysis, and Hoechst 33342 staining, and reactive oxygen species (ROS) measurement were used. Results: IL-1β induced expression of inflammatory cytokines and triggered degradation of the extracellular matrix of rat chondrocytes, but this effect was significantly attenuated by rIL-37 treatment. Enhanced ROS generation following IL-1β stimulation was reduced in a dose-dependent manner after stimulation with rIL-37. IL-1β induced pro-apoptotic markers and suppressed anti-apoptotic markers in rat chondrocytes. Flow cytometry using annexin V-FITC/PI revealed that IL-1β increased the apoptosis rate of rat chondrocytes, and that this effect was markedly reversed by treatment with rIL-37. Conclusions: IL-37 potently attenuated IL-1β-mediated apoptosis of rat chondrocytes by blocking ROS production. This study suggests that IL-37 can serve as a novel anti-cytokine therapy in OA by blocking chondrocyte apoptosis.

Knowledge, Attitudes, and Practices of Patients with Knee Osteoarthritis Regarding Osteoporosis and Its Prevention: A Cross-Sectional Study in China

Background

Older age and female sex are risk factors for osteoarthritis and osteoporosis (OP). This study evaluated the knowledge, attitudes, and practices of patients with knee osteoarthritis (KOA) in China regarding OP and its prevention. This cross-sectional, questionnaire-based study enrolled patients with KOA at four grade-A tertiary hospitals in Shandong Province between 1st September and 20th November 2022.

Methods

The administered questionnaire contained 55 items across four dimensions (demographic information, knowledge, attitude, and practice). Logistic regression analyses were performed to identify factors associated with an overall questionnaire score ≥70% of the maximum possible score. SPSS 26.0 was used for the analyses; P<0.05 was considered significant.

Results

The analysis included 434 participants (261 females). The median knowledge, attitude, and practice scores were 7 (interquartile range: 5-10) (possible range, 0-17 points), 44 (interquartile range: 42-49) (possible range, 11-55 points), and 43 (interquartile range: 38-47) (possible range, 13-65 points), respectively. Multivariable logistic regression indicated that female sex (odds ratio [OR], 2.421; 95% confidence interval [95% CI] 1.558-3.762; P<0.001), age 56-65 years-old (OR, 4.222; 95% CI, 1.763-10.109; P=0.001 vs ≤55 years-old), age >65 years-old (OR, 4.358; 95% CI, 1.863-10.195; P=0.001 vs ≤55 years-old), middle/high/technical secondary school education (OR, 1.853; 95% CI, 1.002-3.428; P=0.049 vs primary school or below), and having KOA for 4-5 years (OR, 2.682; 95% CI, 1.412-5.094; P=0.003 vs ≤3 years) were independently associated with a high KAP score.

Conclusion

There is room for improvement in the knowledge and practices of patients with osteoarthritis in China regarding OP. The findings of this study may facilitate the design and implementation of education programs to increase awareness about OP prevention among patients with KOA.

Removal of the infrapatellar fat pad and associated synovium benefits female guinea pigs in the Dunkin Hartley model of idiopathic osteoarthritis

Background

Several tissues contribute to the onset and advancement of knee osteoarthritis (OA). One tissue type that is worthy of closer evaluation, particularly in the context of sex, is the infrapatellar fat pad (IFP). We previously demonstrated that removal of the IFP had short-term beneficial effects for a cohort of male Dunkin-Hartley guinea pigs. The present project was designed to elucidate the influence of IFP removal in females of this OA-prone strain. It was hypothesized that resection of the IFP would reduce the development of OA in knees of a rodent model predisposed to the disease.

Methods

Female guinea pigs (n=16) were acquired at an age of 2.5 months. Surgical removal of the IFP and associated synovium complex (IFP/SC) was executed at 3 months of age. One knee had the IFP/SC resected; a comparable sham surgery was performed on the contralateral knee. All animals were subjected to voluntary enclosure monitoring and dynamic weight-bearing, as well as compulsory treadmill-based gait analysis monthly; baseline data was collected prior to surgery. Guinea pigs were euthanized at 7 months. Knees from eight animals were evaluated via histology, mRNA expression, and immunohistochemistry (IHC); knees from the remaining eight animals were allocated to microcomputed tomography (microCT), biomechanical analyses (whole joint testing and indentation relaxation testing), and atomic absorption spectroscopy (AAS).

Results

Fibrous connective tissue (FCT) replaced the IFP/SC. Mobility/gait data indicated that unilateral IFP/SC removal did not affect bilateral hindlimb movement. MicroCT demonstrated that osteophytes were not a significant feature of OA in this sex; however, trabecular thickness (TbTh) in medial femorae decreased in knees containing the FCT. Histopathology scores were predominantly influenced by changes in the lateral tibia, which demonstrated that histologic signs of OA were increased in knees containing the native IFP/SC versus those with the FCT. Similarly, indentation testing demonstrated higher instantaneous and equilibrium moduli in the lateral tibial articular cartilage of control knees with native IFPs. AAS of multiple tissue types associated with the knee revealed that zinc was the major trace element influenced by removal of the IFP/SC.

Conclusions

Our data suggest that the IFP/SC is a significant component driving knee OA in female guinea pigs and that resection of this tissue prior to disease has short-term benefits. Specifically, the formation of the FCT in place of the native tissue resulted in decreased cartilage-related OA changes, as demonstrated by reduced Osteoarthritis Research Society International (OARSI) histology scores, as well as changes in transcript, protein, and cartilage indentation analyses. Importantly, this model provides evidence that sex needs to be considered when investigating responses and associated mechanisms seen with this intervention.

Factors influencing the posterior cruciate ligament buckling phenomenon-a multiple linear regression analysis of bony and soft tissue structures of the knee joint

PURPOSE

To determine whether posterior cruciate ligament (PCL) buckling (angular change) is associated with anterior cruciate ligament (ACL) status (intact or ruptured), meniscal bone angle (MBA), anterior tibial translation (ATT), body weight, femoral-tibial rotation (FTR), posterior tibial slope (PTS), PCL length and femoral-tibial distance (FTD) and to identify the factors that have the greatest influence.

METHODS

All enrolled participants were scanned with a 3.0 T, 8-channel coil MRI system (Magnetom Verio; Siemens). Bone and soft tissue parameters were measured by MIMICS software for each subject and each measured parameter was correlated with PCL buckling phenomena. The correlated and statistically significant parameters were then analyzed by multiple linear regression to determine the magnitude of the effect of the different parameters on the PCL buckling phenomenon.

RESULTS

A total of 116 subjects (50 ACL ruptured and 66 age, weight and height matched volunteers with uninjured knees) were enrolled. Among all measured parameters, there were 8 parameters that correlated with PCL angle (PCLA), of which ACL status had the strongest correlation with PCLA (r = - 0.67, p =  < 0.001); and 7 parameters that correlated with PCL-posterior femoral cortex angle (PCL-PCA), of which ATT had the strongest correlation with PCL-PCA (r = 0.69, p =  < 0.001). PCLIA was not significantly correlated with any of the measured parameters. Multiple linear regression analyses revealed four parameters can explain PCLA, of which ACL status had the strongest effect on PCLA (absolute value of standardized coefficient Beta was 0.508). Three parameters can explain PCL-PCA, of which ATT had the strongest effect on PCLIA (r = 0.69, p = < 0.001), ATT has the greatest effect on PCL-PCA (absolute value of normalized coefficient Beta is 0.523).

CONCLUSIONS

PCLA may be a simple and easily reproducible and important supplement for the diagnosis of ACL injury; PCL-PCA is a simple and easily reproducible and important complementary tool for the detection of ATT. The use of PCLA is more recommended to aid in the diagnosis of ACL injury.

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.

Does Walking Have an Association with Osteoarthritis? A Two-Sample Mendelian Randomization Analysis

Objective

Osteoarthritis (OA) is one of the major disabling human diseases. The related studies indicate a potential correlation between walking and OA. However, there is still a lack of evidence in genetics to support the correlation between walking and OA. Therefore, this study aimed to explore the relationship between walking and OA at the genetic level.

Methods

The publicly available Genome Wide Association Study (GWAS) data were used, with inverse variance weighting (IVW, the random-effects model) as the main analysis method, whereas MR-Egger, Weighted median, Simple mode, and Weighted mode as the secondary analysis methods. In addition, Cochran's Q test, pleiotropy test, and MR-Egger intercept test were conducted to examine the heterogeneity and pleiotropy of the outcome.

Results

In the MR analysis, IVW results showed a negative correlation between types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) and OA (KOA or HOA) (odds ratio (OR) = 0.3224, 95% confidence interval (CI): 0.1261 to 0.8243), and the difference was of statistical significance (P = 0.0181). Moreover, IVW results also revealed a negative correlation between types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) and KOA (OR = 0.1396, 95% CI: 0.0484 to 0.4026), and the difference was statistically significant (P = 0.0003). However, IVW results did not demonstrate any statistical significance types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) and HOA (OR = 1.2075, 95% CI: 0.1978 to 7.3727, P = 0.8381).

Conclusion

From genetic studies, types of physical activity in last 4 weeks: Walking for pleasure (not as a means of transport) is negatively correlated with knee osteoarthritis (KOA), but there is no clear evidence supporting its correlation with hip osteoarthritis (HOA).

Effects of a Combination of Polynucleotide and Hyaluronic Acid for Treating Osteoarthritis

Knee osteoarthritis (OA), an age-related degenerative disease characterized by severe pain and disability, is treated using polynucleotides (PNs) and hyaluronic acid (HA). The intra-articular (IA) injection of HA has been studied extensively in both animal models and in humans; however, the efficacy and mechanisms of action remain unclear. In addition, there has been a paucity of research regarding the use of PN alone or in combination with HA in OA. To investigate the effect of the combined injection of PN and HA in vivo, pathological and behavioral changes were assessed in an OA model. Anterior cruciate ligament transection and medial meniscectomy were performed in Sprague-Dawley rats to create the OA animal model. The locomotor activity improved following PNHA injection, while the OARSI grade improved in the medial tibia and femur. In mild OA, TNFα levels decreased histologically in the PN, HA, and PNHA groups but only the PNHA group showed behavioral improvement in terms of distance. In conclusion, PNHA exhibited anti-inflammatory effects during OA progression and improved locomotor activity regardless of the OARSI grade.

Anterior Intercondylar Notch Geometry in Relation to the Native Anterior Cruciate Ligament Size

BACKGROUND

The intercondylar notch (ICN) and the anterior cruciate ligament (ACL) are important structures in knee morphometry, with key roles in stabilizing the knee.

AIM

To determine the associations between the specific shape of the ICN (A-, W-, or U-shape) and the ACL size in patients with intact ACLs.

METHODS

Magnetic resonance imaging (MRI) scans were independently analyzed by two experts: one orthopedic surgeon and one imaging physician. In all cases, the following measurements were taken based on the existing definitions: ACL area, anterior ICN (aICN) area, ICN width, lateral trochlear inclination (LTI), and Insall-Salvati index.

RESULTS

A total of 65 cases (50.8% male; 33.8 ± 10.2 years mean age at inclusion) were included in the study. The ACL and aICN areas were significantly larger in patients with U-shaped compared with A-shaped and W-shaped ICNs: 0.50 (0.20-0.80) vs. 0.40 (0.20-0.80) vs. 0.40 (0.30-0.80), p = 0.011 and 1.16 (0.57-3.60) vs. 0.47 (0.15-0.95) vs. 0.37 (0.15-0.81), p < 0.001, respectively. Internal meniscal lesions were more common in cases with U-shaped ICNs (64.0%), while external ones were more common in W-shaped ICN cases (35.3%). None of the A-shaped cases had external chondral or meniscal lesions. The ACL area was significantly larger in males and internal meniscal injuries, with no differences between chondral lesions, external meniscal injuries, patellar chondral lesions, patella alta, or trochlear dysplasia.

CONCLUSION

The specific shape of the intercondylar notch was associated with the anterior cruciate ligament-anterior intercondylar notch (ACL-aICN) area size correlation, with a strong correlation between ACL and aICN area when the intercondylar notch was A-shaped or W-shaped, and a low correlation when the notch was U- shaped. The specific shape of the intercondylar notch (A-, W-, or U-shape) was associated with the occurrence of both internal and external meniscal injuries, with the U-shaped intercondylar notch morphometry being more frequent in cases with internal meniscal injuries and the W-shape being more common in cases with external meniscal injuries.

Assessment of the Impact of Physical Activity on the Musculoskeletal System in Early Degenerative Knee Joint Lesions in an Animal Model

Osteoarthritis (OA) is one of the most prevalent diseases of the osteoarticular system. Progressive destruction of joints is accompanied by development of pathological changes in the muscle tissue, i.e., weakening, atrophy, and remodelling (sarcopenia). The aim of the present study is to assess the impact of physical activity on the musculoskeletal system in an animal model of early degenerative lesions in the knee joint. The study involved 30 male Wistar rats. The animals were allocated to three subgroups of 10 animals each. Each animal from the three subgroups received sodium iodoacetate by injection into the patellar ligament of the right knee joint, whereas saline was administered through the patellar ligament in the left knee joint. The rats in the first group were stimulated to exercise on a treadmill. The animals in the second group were allowed to lead a natural lifestyle (no treadmill stimulation). In the third group, all parts of the right hind limb muscle were injected with Clostridium botulinum toxin type A. The study demonstrated that, compared to the active rats, bone density in the immobilised rats decreased, as indicated by the densitometric assessment of the whole body and the examination of rats' hind limbs and knee joints alone. This clearly evidenced the impact of physical activity on bone mineralisation. The weight of both fat and muscle tissues in the physically inactive rats was reduced. Additionally, the adipose tissue had higher weight in the entire right hind limbs, where monoiodoacetic acid was administered to the knee joint. The animal model clearly showed the importance of physical activity in the early stages of OA, as it slows down the process of joint destruction, bone atrophy, and muscle wasting, whereas physical inactivity contributes to progression of generalised changes in the musculoskeletal system.

Early removal of the infrapatellar fat pad/synovium complex beneficially alters the pathogenesis of moderate stage idiopathic knee osteoarthritis in male Dunkin Hartley guinea pigs

BACKGROUND

The infrapatellar fat pad (IFP) is the largest adipose deposit in the knee; however, its contributions to the homeostasis of this organ remain undefined. To determine the influence of the IFP and its associated synovium (IFP/synovium complex or IFP/SC) on joint health, this study evaluated the progression of osteoarthritis (OA) following excision of this unit in a rodent model of naturally-occurring disease.

METHODS

Male Dunkin-Hartley guinea pigs (n=18) received surgical removal of the IFP in one knee at 3 months of age; contralateral knees received sham surgery as matched internal controls. Mobility and gait assessments were performed prior to IFP/SC removal and monthly thereafter. Animals were harvested at 7 months of age. Ten set of these knees were processed for microcomputed tomography (microCT), histopathology, transcript expression analyses, and immunohistochemistry (IHC); 8 sets of knees were dedicated to microCT and biomechanical testing (material properties of knee joints tissues and anterior drawer laxity).

RESULTS

Fibrous connective tissue (FCT) developed in place of the native adipose depot. Gait demonstrated no significant differences between IFP/SC removal and contralateral hindlimbs. MicroCT OA scores were improved in knees containing the FCT. Quantitatively, IFP/SC-containing knees had more osteophyte development and increased trabecular volume bone mineral density (vBMD) in femora and tibiae. Histopathology confirmed maintenance of articular cartilage structure, proteoglycan content, and chondrocyte cellularity in FCT-containing knees. Transcript analyses revealed decreased expression of adipose-related molecules and select inflammatory mediators in FCTs compared to IFP/SCs. This was verified via IHC for two key inflammatory agents. The medial articular cartilage in knees with native IFP/SCs showed an increase in equilibrium modulus, which correlated with increased amounts of magnesium and phosphorus.

DISCUSSION/CONCLUSION

Formation of the FCT resulted in reduced OA-associated changes in both bone and cartilage. This benefit may be associated with: a decrease in inflammatory mediators at transcript and protein levels; and/or improved biomechanical properties. Thus, the IFP/SC may play a role in the pathogenesis of knee OA in this strain, with removal prior to disease onset appearing to have short-term benefits.