Osteoarthritis-patterns, cardio-metabolic risk factors and risk of all-cause mortality: 20 years follow-up in patients after hip or knee replacement

Association between cardiovascular health and all-cause mortality risk in patients with osteoarthritis

BACKGROUND

This study was to explore the relationship between cardiovascular health (CVH) and the risk of all-cause mortality in patients with osteoarthritis (OA).

METHODS

This cohort study retrieved the data of 3642 patients with OA aged ≥ 20 years from the 2007-2018 National Health and Nutrition Examination Survey (NHANES). CVH was evaluated based on Life's Essential 8 (LE8) includes diet, physical activity, nicotine exposure, sleep health, body mass index, blood lipids, blood glucose, and blood pressure. The outcome of all-cause mortality was assessed using the death certificate records of participants from the National Death Index. Variables that might affect all-cause mortality were used as covariates. The weighted univariate COX proportional hazards model was used to explore the association between each covariate and all-cause mortality. The weighted univariate and multivariate COX proportional hazards models were used to explore the association between different CVH levels and all-cause mortality. A restricted cubic spline (RCS) curve was plotted to show the association between different CVH levels and all-cause mortality in OA patients. Hazard ratio (HR) and 95% confidence interval (CI) were calculated.

RESULTS

Findings show that people with moderate CVH (HR = 0.67, 95% CI = 0.45-0.98) and high CVH (HR = 0.47, 95% CI = 0.26-0.87) were associated with reduced risk of all-cause mortality in patients with OA. The HR of all-cause mortality in patients with OA decreased by 0.12 as per 10 points increase of LE8 score (HR = 0.81, 95% CI = 0.73-0.90). The RCS curve revealed that the HR of all-cause mortality decreased with the increase in LE8 score. The survival probability of patients in the high CVH group was higher than the moderate CVH group and low CVH group (p = 0.002).

CONCLUSION

Moderate-to-high CVH is associated with a decreased risk of all-cause mortality in patients with OA. These findings might provide a reference for the formulation of prognosis improvement strategies for the management of patients with OA.

J-shaped association of serum uric acid concentrations with all-cause mortality in individuals with osteoarthritis: A prospective cohort study

OBJECTIVE

The purpose of this study was to explore the relationship between serum uric acid (SUA) concentrations and all-cause mortality in individuals with osteoarthritis (OA).

METHODS

All participant data were retrieved from the National Health and Nutrition Examination Survey database. A total of 4671 participants (age range: 20 to 85 years old), including 2988 females and 1683 males, were included in this study. The determination of death outcome was based on the National Death Index (up to December 31, 2019). We explored the nonlinear relationship between SUA concentrations and all-cause mortality in OA patients by establishing a Cox proportional risk model and a two-segment Cox proportional risk model and ran an interaction test to identify the high-risk population for all-cause mortality.

RESULTS

During 30,645 person-years of follow-up, the number of all-cause deaths for females and males was 736 and 516, respectively. After multivariate adjustment, we found a nonlinear relationship between SUA concentrations and all-cause mortality in both females and males with OA. In addition, we found a J-shaped relationship between SUA concentrations and all-cause mortality. The SUA concentration thresholds for all-cause mortality of females and males were stable at 5.6mg/dl and 6.2mg/dl, respectively. Compared with SUA concentrations below the inflection point, the all-cause mortality risk at higher SUA concentrations in females and males with OA increased by 20% (hazard ratio [HR]: 1.2, 95% confidence interval [CI]: 1.1 to 1.2) and 25% (HR: 1.2, 95% CI: 1.12 to 1.39), respectively.

CONCLUSIONS

There is a nonlinear relationship between SUA concentrations and all-cause mortality in the American OA population (J-shaped association). The all-cause mortality thresholds for SUA concentrations in females and males are 5.6mg/dl and 6.2mg/dl, respectively.

30-day to 10-year mortality rates following total hip arthroplasty: a meta-analysis of the last decade (2011-2021)

BACKGROUND

Mortality after total hip arthroplasty (THA) is a rare but devastating complication. This meta-analysis aimed to: (1) determine the mortality rates at 30 days, 90 days, 1 year, 5 years and 10 years after THA; (2) identify risk factors and causes of mortality after THA.

METHODS

Pubmed, MEDLINE, Cochrane, EBSCO Host, and Google Scholar databases were queried for studies reporting mortality rates after primary elective, unilateral THA. Inverse-proportion models were constructed to quantify the incidence of all-cause mortality at 30 days, 90 days, 1 year, 5 years and 10 years after THA. Random-effects multiple regression was performed to investigate the potential effect modifiers of age (at time of THA), body mass index, and gender.

RESULTS

A total of 53 studies (3,297,363 patients) were included. The overall mortality rate was 3.9%. The 30-day mortality was 0.49% (95% CI; 0.23-0.84). Mortality at 90 days was 0.47% (95% CI, 0.38-0.57). Mortality increased exponentially between 90 days and 5 years, with a 1-year mortality rate of 1.90% (95% CI, 1.22-2.73) and a 5-year mortality rate of 9.85% (95% CI, 5.53-15.22). At 10-year follow-up, the mortality rate was 16.43% (95% CI, 1.17-22.48). Increasing comorbidity indices, socioeconomic disadvantage, age, anaemia, and smoking were found to be risk factors for mortality. The most commonly reported causes of death were ischaemic heart disease, malignancy, and pulmonary disease.

CONCLUSIONS

All-cause mortality remains low after contemporary THA. However, 1 out of 10 patients and 1 out of 6 patients were deceased after 5 years and 10 years of THA, respectively. As expected, age, but not BMI or gender, was significantly associated with mortality.

IL-1β inhibition combined with cholesterol-lowering therapies decreases synovial lining thickness and spontaneous cartilage degeneration in a humanized dyslipidemia mouse model

INTRODUCTION

Both systemic inflammation and dyslipidemia contribute to osteoarthritis (OA) development and have been suggested as a possible link between metabolic disease and OA development. Recently, the CANTOS trial showed a reduction in knee and hip replacements after inhibition of IL-1β in patients with a history of cardiovascular disease and high inflammatory risk. In this light, we investigated whether inhibition of IL-1β combined with cholesterol-lowering therapies can reduce OA development in dyslipidemic APOE∗3Leiden mice under pro-inflammatory dietary conditions.

MATERIALS AND METHODS

Female ApoE3∗Leiden mice were fed a cholesterol-supplemented Western-Type diet (WTD) for 38 weeks. After 14 weeks, cholesterol-lowering and anti-inflammatory treatments were started. Treatments included atorvastatin alone or with an anti-IL1β antibody, and atorvastatin combined with proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitor alirocumab without or with the anti-IL1β antibody. Knee joints were analyzed for cartilage degradation, synovial inflammation and ectopic bone formation using histology at end point.

RESULTS

Cholesterol-lowering treatment successfully decreased systemic inflammation in dyslipidemic mice, which was not further affected by inhibition of IL-1β. Synovial thickening and cartilage degeneration were significantly decreased in mice that received cholesterol-lowering treatment combined with inhibition of IL-1β (P < 0.01, P < 0.05, respectively) compared to mice fed a WTD alone. Ectopic bone formation was comparable between all groups.

CONCLUSION

These results indicate that inhibition of IL-1β combined with cholesterol-lowering therapy diminishes synovial thickening and cartilage degeneration in mice and may imply that this combination therapy could be beneficial in patients with metabolic inflammation.

Knee Osteoarthritis in Relation to the Risk Factors of the Metabolic Syndrome Components and Environment of Origin

Background: Knee osteoarthritis (KOA) is a chronic degenerative pathology that is associated with multiple risk factors such as age, sex, obesity, or metabolic syndrome (MetS). The present clinical trial aimed to investigate the influence of the environment of origin, body mass index (BMI), and MetS parameters on the KOA differentiated degrees. Methods: 85 patients were admitted for the clinical study. The KOA presence was investigated using X-rays analysis. The Kellgren−Lawrence classification (KL) of the KOA severity and the MetS characteristic parameters using freshly collected blood were performed for each patient. All data collected were used for ANOVA statistic interpretation. Results: The total cholesterol and glycemia were found to be statistically significant (p < 0.028, and p < 0.03, respectively), with a high level in patients with severe KOA compared to healthy ones. Patients from rural regions are 5.18 times more prone to develop severe KOA when compared to ones from urban areas. Conclusions: The results of the statistical analysis confirmed the correlation between the incidence and severity of KOA and the influence of increased values of BMI, glycemia, triglycerides, and total cholesterol. The investigations revealed a statistically significant influence of the environment of origin on the KOA degree of the patients.

Preoperative health-related quality of life is independently associated with postoperative mortality risk following total hip or knee arthroplasty : seven to eight years' follow-up

AIMS

The primary aim was to assess whether preoperative health-related quality of life (HRQoL) was associated with postoperative mortality following total hip arthroplasty (THA) and knee arthroplasty (KA). Secondary aims were to assess whether patient demographics/comorbidities and/or joint-specific function were associated with postoperative mortality.

METHODS

Patients undergoing THA (n = 717) and KA (n = 742) during a one-year period were identified retrospectively from an arthroplasty register. Patient demographics, comorbidities, Oxford score, and EuroQol five-dimension (EQ-5D) were recorded preoperatively. Patients were followed up for a minimum of seven years and their mortality status was obtained. Cox regression analysis was used to adjust for confounding.

RESULTS

During the study period, 111 patients (15.5%) undergoing THA and 135 patients (18.2%) undergoing KA had died at a mean follow-up of 7.5 years (7 to 8). When adjusting for confounding, the preoperative EQ-5D was associated with postoperative mortality, and for each 0.1 difference in the utility there was an associated change in mortality risk of 6.7% (p = 0.048) after THA, and 6.8% (p = 0.047) after KA. Comorbidities of connective tissue disease (p ≤ 0.026) and diabetes (p ≤ 0.028) were associated with mortality after THA, whereas MI (p ≤ 0.041), diabetes (p ≤ 0.009), and pain in other joints (p ≤ 0.050) were associated with mortality following KA. The preoperative Oxford score was associated with mortality, and for each one-point change in the score there was an associated change in mortality risk of 2.7% (p = 0.025) after THA and 4.3% (p = 0.003) after KA.

CONCLUSION

Worse preoperative HRQoL and joint specific function were associated with an increased risk of postoperative mortality. Both HRQoL and joint-specific function decline with longer waiting times to surgery for THA and KA and therefore may result in an increased postoperative mortality risk than would have been expected if surgery had been undertaken earlier.Cite this article: Bone Jt Open 2022;3(12):933-940.

The repair effect and mechanism of continuous passive motion on osteoarthritis in a rabbit model

OBJECTIVE

To observe the effect of continuous passive motion (CPM) on osteoarthritis in a rabbit model and explore its mechanism.

METHODS

Thirty healthy rabbits with a total of 60 knee joints were randomized into three groups. Group A had CPM for 8 h daily, starting on postoperative day 1 and free movement in the cage, group B received CPM for 2 h daily, starting on postoperative day 1 and free movement in the cage, and group C only had free movement in the cage. Mankin's score was used to compare the gross morphology of the rabbit's knee joint. Malondialdehyde (MDA) and superoxide dismutase (SOD) were measured by RT-PCR and western blot method before and after intervention.

RESULTS

The Mankin's scores of rabbits in groups A and B were significantly lower than those in group C, and those in group A were lower than those in group B at week 4 and week 12 of intervention (P<0.05). At week 4 of the CPM intervention, the gross morphological scores were the highest in group A, followed by group B, and the lowest in group C (P<0.05). At week 12 of CPM intervention, the gross morphological scores of the knee joints in groups A and B were increased again, which were the highest in group A, followed by group B, and the lowest in group C (P<0.05). At week 12 of intervention, MDA levels in group A were lower than those in groups B and C, whereas SOD levels in group A were higher than those in groups B and C.

CONCLUSION

CPM can effectively improve the symptoms of knee osteoarthritis in rabbits and increase the mobility of the joints, and the mechanism may be related to the ability of CPM to reduce the overproduction of peroxide at the lesion site.

Novel high-intensive cholesterol-lowering therapies do not ameliorate knee OA development in humanized dyslipidemic mice

OBJECTIVE

High systemic cholesterol levels have been associated with osteoarthritis (OA) development. Therefore, cholesterol lowering by statins has been suggested as a potential treatment for OA. We investigated whether therapeutic high-intensive cholesterol-lowering attenuated OA development in dyslipidemic APOE∗3Leiden.CETP mice.

METHODS

Female mice (n = 13-16 per group) were fed a Western-type diet (WTD) for 38 weeks. After 13 weeks, mice were divided into a baseline group and five groups receiving WTD alone or with treatment: atorvastatin alone, combined with PCSK9 inhibitor alirocumab and/or ANGPTL3 inhibitor evinacumab. Knee joints were analysed for cartilage degradation, synovial inflammation and ectopic bone formation using histology. Aggrecanase activity in articular cartilage and synovial S100A8 expression were determined as markers of cartilage degradation/regeneration and inflammation.

RESULTS

Cartilage degradation and active repair were significantly increased in WTD-fed mice, but cholesterol-lowering strategies did not ameliorate cartilage destruction. This was supported by comparable aggrecanase activity and S100A8 expression in all treatment groups. Ectopic bone formation was comparable between groups and independent of cholesterol levels.

CONCLUSIONS

Intensive therapeutic cholesterol lowering per se did not attenuate progression of cartilage degradation in dyslipidemic APOE∗3Leiden.CETP mice, with minor joint inflammation. We propose that inflammation is a key feature in the disease and therapeutic cholesterol-lowering strategies may still be promising for OA patients presenting both dyslipidemia and inflammation.

An implementation study of periarticular knee osteotomy in the treatment of knee osteoarthritis

OBJECTIVE

To analyze the clinical effects of periarticular knee osteotomy (PKO) in the treatment of knee osteoarthritis (KOA).

METHODS

A total of 180 patients with KOA admitted to our hospital were selected as the study subjects, and were divided into study group (90 cases) and control group (90 cases) in accordance with different intervention measures. The study group was treated with PKO, while the control group was treated with joint replacement. The perioperative indices, and postoperative pain degrees, knee joint function, quality of life, inflammatory factors and complications were compared between the two groups.

RESULTS

The control group was superior to the study group regarding the amount of preoperative bleeding, surgical duration, and incidence rate of complications, while the study group was superior to the control group regarding the long-term (over 2 years) knee joint function and quality of life (P < 0.05). There was no marked difference in the postoperative pain degrees and preoperative and postoperative levels of inflammatory factors between the two groups (P < 0.05).

CONCLUSION

PKO, exhibiting a high safety profile, can remarkably improve the joint pain symptoms, knee joint function, quality of life and symptoms of KOA in patients with KOA. Therefore, PKO is worthy of clinical promotion and implementation.

Relationship between cardiac biomarker concentrations and long-term mortality in subjects with osteoarthritis

Osteoarthritis (OA) is associated with adverse cardio-metabolic features. N-terminal pro-B-type natriuretic peptide (NT-proBNP) and high-sensitivity troponins T and I (hs-cTnT and hs-cTnI) are well-characterized cardiac markers and provide prognostic information. The objective was to assess the association of cardiac biomarker concentrations with long-term mortality in subjects with OA. In a cohort of 679 OA subjects, undergoing hip or knee replacement during 1995/1996, cardiac biomarkers were measured and subjects were followed over 20 years. During a median follow-up of 18.4 years, 332 (48.9%) subjects died. Median of hs-cTnT, hs-cTnI, and NT-proBNP at baseline was 3.2 ng/L, 3.9 ng/L, and 96.8 ng/L. The top quartile of NT-proBNP was associated with increased risk of mortality (Hazard Ratio (HR) 1.79, 95% confidence interval (CI) 1.17–2.73) after adjustment for covariates including troponins (hs-cTnT HR 1.30 (95% CI 0.90–1.89), hs-cTnI HR 1.32 (95% CI 0.87–2.00) for top category). When biomarker associations were evaluated as continuous variables, only NT-proBNP (HR per log-unit increment 1.34, 95% CI 1.16–1.54) and hs-cTnI (HR 1.38, 95% CI 1.11–1.72) showed robust results. Elevated cardiac biomarker concentrations predicted an increased risk of long-term mortality and strongest for NT-proBNP and hs-cTnI. These results might help to identify subjects at risk and target preventive efforts early.

Palmatine as an Agent Against Metabolic Syndrome and Its Related Complications: A Review

Palmatine is a naturally occurring isoquinoline alkaloid with various pharmacological properties. Given its antioxidant and anti-inflammatory properties, palmatine may be able to impede the effects of metabolic syndrome (MetS) and its related diseases triggered by inflammation and oxidative stress. This review summarises the existing literature about the effects of palmatine supplementation on MetS and its complications. The evidence shows that palmatine could protect against MetS, and cardiovascular diseases, osteoporosis and osteoarthritis, which might be associated with MetS. These protective effects are mediated by the antioxidant and anti-inflammatory properties of palmatine. Although preclinical experiments have demonstrated the efficacy of palmatine against MetS and its related diseases, no human clinical trials have been performed to validate these effects. This research gap should be bridged to validate the efficacy and safety of palmatine supplementation in protecting humans against MetS and its related diseases.

Growth Differentiation Factor-15 as a Potent Predictor of Long-Term Mortality among Subjects with Osteoarthritis

Background: Subjects with osteoarthritis (OA) are at increased risk for cardiovascular (CV) and all-cause mortality. Whether biomarkers improve outcome prediction in these patients remains to be elucidated. We investigated the association between growth differentiation factor 15 (GDF-15), a novel stress-responsive cytokine, and long-term all-cause mortality among OA patients. Methods: Within the Ulm Osteoarthritis Study, GDF-15 has been measured in the serum of 636 subjects, who underwent hip or knee arthroplasty between 1995 and 1996 (median age 65 years). Results: During a median follow-up of 19.7 years, a total of 402 deaths occurred. GDF-15 was inversely associated with walking distance. Compared to the bottom quartile (Q), subjects within the top quartile of GDF-15 demonstrated a 2.69-fold increased risk of dying (hazard ratio (HR) (95% confidence interval (CI)) 2.69 (1.82–3.96) adjusted for age, sex, BMI, smoking status, localization of OA, diabetes, maximum walking distance, total cholesterol, and cystatin C. Further adjustment for NT-proBNP, troponin I, and hs-C-reactive protein did not change the results appreciably (HR (95%CI) 1.56 (1.07–2.28); 1.75 (1.21–2.55); 2.32 (1.55–3.47) for Q2, Q3, and Q4 respectively, p for trend < 0.001). Conclusions: In subjects with OA, GDF-15 represents a potent predictor of decreased survival over >20 years, independently of conventional CV risk factors, renal, cardiac, and inflammatory biomarkers as well as walking disability, previously associated with increased mortality and lower extremity OA.

Five years' trajectories of functionality and pain in patients after hip or knee replacement and association with long-term patient survival

To describe the 5 years’ trajectories in functionality and pain of patients with hip or knee osteoarthritis and arthroplasty and analyze the association of these with long-term patients survival. Patients with OA receiving total hip or knee arthroplasty were recruited and completed two sets of standardized questionnaires for functionality and pain 6, 12, and 60 months postoperatively. Multivariate mixed models were conducted to assess trajectories over time and the resulting improvement per month during the last time period was included in a landmark-model to estimate adjusted hazard ratios for mortality. In total 809 patients with joint replacement were included (mean age 65.0 years, 62.2% female), 407 patients died (median follow-up 18.4 years). Both instruments of functionality and pain showed extensive improvement during the first 6 months. Baseline and change in functionality (both p < 0.001) and pain (p = 0.02) during the first 6 months were associated with mortality. Better values in functionality corresponded with improved survival whereas the association with the pain scores was inverse. In patients with hip and knee OA, an explicit improvement in function is seen within the first 6 months after arthroplasty. In addition, especially the functionality scores at baseline as well as their improvement showed an association with long-term patient survival.

Gender Differences between Multimorbidity and All-Cause Mortality among Older Adults

Objectives

This study seeks to determine the prevalence of chronic diseases and analyze the association between multimorbidity and all-cause mortality by sex.

Methods

This is a 16-year longitudinal study of follow-up. We used sample data of the SABE (Health, Well-Being and Aging) study cohort and mortality data obtained through the Mortality Information Improvement Program of the City of São Paulo (PRO-AIM) from the 2000–2016 period. Survival analysis was performed using Cox proportional hazard models.

Results

Hypertension (HT) was the most prevalent disease in older adults (52.93%), followed by musculoskeletal disorders (MSDs) (27.09%), cardiovascular diseases (CD) (17.79%), diabetes mellitus (DM) (16.95%), mental disorders (MD) (15.43%), and respiratory diseases (RD) (9.72%). The highest mortality rate in women was observed in the combination of HT/MSDs/DM/MD (HR = 6.15, 95% CI = 2.32, 16.32), while in men was in the combination of HT/CD/MSDs/DM (HR = 5.72, 95% CI = 1.72, 19.06).

Conclusion

Similar to previous studies carried out in developed countries, we found that all-cause mortality increased as diseases are added to an individual. Women and men presented different mortality patterns according to multimorbidity. Therefore, we suggest that additional longitudinal studies should be performed in order to analyze mortality by sex.

Serum Cartilage Oligomeric Matrix Protein in Late-Stage Osteoarthritis: Association with Clinical Features, Renal Function, and Cardiovascular Biomarkers

This study aimed to assess associations between serum cartilage oligomeric matrix protein (sCOMP) and phenotypic characteristics in late-stage hip and knee Osteoarthritis (OA) as well as its correlation with further serum markers of possible comorbidities in the Ulm Osteoarthritis Study. Moreover, the prognostic relevance of preoperative sCOMP concentrations for short-term functionality and pain outcomes after hip or knee joint replacement was explored. Preoperative serum samples and detailed information about the health status (i.e., WOMAC scores, Hannover Functionality Status (FFbH)) of 754 OA patients undergoing total joint replacement were included. Spearman rank-correlation coefficients and multiple linear regression models were used to evaluate the relationships between sCOMP, other serum markers, and health outcomes. There was a significant positive association between sCOMP and markers of renal (cystatin C, creatinine, and eGFR) and cardiac (e.g., NT-proBNP) impairment. Since renal failure might cause accumulation of sCOMP, additional adjustment with eGFR was performed. Preoperative sCOMP levels in knee OA but not hip OA patients were positively associated with FFbH, WOMAC function sub-scale and total WOMAC scale as well as the post-operative WOMAC stiffness sub-scale six months after surgery. Our data clearly demonstrate an association between sCOMP and renal function as well as other confounding factors, which should be considered in future biomarker studies.

Different Secretory Activity of Articular and Subcutaneous Adipose Tissues from Rheumatoid Arthritis and Osteoarthritis Patients

Rheumatoid arthritis (RA) and osteoarthritis (OA) are characterized by joint and systemic high- or low-grade inflammation, respectively. Adipose tissue (AT) may contribute to the pathogenesis of these diseases. To address this issue, we investigated whether basal and pro-inflammatory cytokine (IL-1β)-triggered release of adipocytokines (TNF, IL-6, IL-10, IL-1Ra, TGFβ, CCL2/MCP-1, CCL5/RANTES, MMP-3) from subcutaneous (ScAT) and intraarticular (AAT) adipose tissues of RA and OA patients mirror differences between these diseases in an intensity of systemic and local inflammation. We found that in both diseases basal adipocytokine release was usually higher from AAT than ScAT, reflecting stronger local than systemic inflammation. However, ScAT secreted considerable amounts of pro- and anti-inflammatory factors as well. Spontaneous secretion of some adipocytokines (MMP-3 and/or TNF, CCL2/MCP-1, IL-1Ra) was higher in osteoarthritis than rheumatoid ATs and probably caused by weaker anti-inflammatory treatment of OA patients. By contrast, reactivity of ATs to IL-1β was significantly lower in OA than RA and IL-1β antagonist (IL-1Ra) could be responsible for this because we found its overproduction in OA ATs. Interestingly, higher reactivity of ScAT than AAT to IL-1β was a characteristic for OA while reactivity of rheumatoid ScAT and AAT to this stimulus was equal. We conclude that differences between OA and RA in reactivity of AAT and ScAT to pro-inflammatory stimulus mimicking in vivo condition reflect dissimilarity in an intensity of disease-specific inflammation and thus support contribution of ATs to these pathological processes. Moreover, we propose that more efficient anti-inflammatory mechanism(s) are preserved in ATs of OA than RA patients.

The Expression of Thrombospondin-4 Correlates with Disease Severity in Osteoarthritic Knee Cartilage

Osteoarthritis (OA) is a progressive joint disease characterized by a continuous degradation of the cartilage extracellular matrix (ECM). The expression of the extracellular glycoprotein thrombospondin-4 (TSP-4) is known to be increased in injured tissues and involved in matrix remodeling, but its role in articular cartilage and, in particular, in OA remains elusive. In the present study, we analyzed the expression and localization of TSP-4 in healthy and OA knee cartilage by reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and immunoblot. We found that TSP-4 protein expression is increased in OA and that expression levels correlate with OA severity. TSP-4 was not regulated at the transcriptional level but we detected changes in the anchorage of TSP-4 in the altered ECM using sequential protein extraction. We were also able to detect pentameric and fragmented TSP-4 in the serum of both healthy controls and OA patients. Here, the total protein amount was not significantly different but we identified specific degradation products that were more abundant in sera of OA patients. Future studies will reveal if these fragments have the potential to serve as OA-specific biomarkers.