Objective. To identify factors that predict a poor physical function outcome over 3 years in individuals with knee osteoarthritis (OA), in an effort to aid in the development of strategies to prevent such functional limitations and consequential disability.Methods. Community-recruited individuals with knee OA underwent baseline, 18-month, and 3-year assessments of candidate risk factors and physical function. Risk factors were age, body mass index (BMI), knee pain intensity (on a visual analog scale [VAS]), local mechanical and neuromuscular factors (varusvalgus laxity, malalignment, proprioceptive inaccuracy, quadriceps strength, hamstring strength), activity level (Physical Activity Scale for the Elderly, amount of aerobic exercise), and psychosocial factors (Short-Form 36 [SF-36] mental health and role-functioning emotional subscales, self-efficacy using the Arthritis SelfEfficacy Scale physical function subscale, and social support using the Medical Outcomes Study Social Support Survey). Outcome was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function scale and rate of chair-stand performance. Participants were grouped by quintile of baseline WOMAC score. The baseline to 3-year outcome was considered "good" when function improved by 1 or more quintiles or remained within the 2 highest function groups, and was considered "poor" when function declined by 1 or more quintiles or remained within the 3 lowest function groups. The same approach was taken for chair-stand outcome. Logistic regression was used to evaluate both the baseline level and the baseline to 18-month change in each factor as a predictor of physical function outcome over 3 years, adjusting for age, BMI, knee pain intensity, disease severity, and additional potential confounders. Results. Factors that significantly increased the likelihood of a poor WOMAC outcome were baseline laxity (crude odds ratio

In persons with knee OA, knee pain severity was associated with subarticular bone attrition, bone marrow lesions, synovitis/effusion, and meniscal tears. The contribution of bone marrow lesions to pain severity appeared to require the presence of bone attrition.

Greater varus-valgus laxity in the uninvolved knees of OA patients versus older control knees and an age-related increase in varus-valgus laxity support the concept that some portion of the increased laxity of OA may predate disease. Loss of cartilage/bone height is associated with greater varus-valgus laxity. These results raise the possibility that varus-valgus laxity may increase the risk of knee OA and cyclically contribute to progression.

Objective. To test the hypothesis that a greater peak internal hip abduction moment is associated with a reduced likelihood of ipsilateral medial tibiofemoral osteoarthritis (OA) progression.Methods. Fifty-seven persons with knee OA (by definite osteophyte presence and symptoms) were evaluated. Baseline assessments included kinematic and kinetic gait parameters, obtained with an optoelectronic camera system and force platform, with inverse dynamics used to calculate 3-dimensional moments at the joints; pain, using a separate visual analog scale for each knee; and alignment, using full-limb radiographs. Radiographs of the knee in a semiflexed position, with fluoroscopic confirmation of tibial rim alignment, were obtained at baseline and 18 months later. Disease progression was defined as worsening of the grade of medial joint space narrowing. Logistic regression obtained with generalized estimating equations was used to estimate odds ratios (ORs) for progression per unit of hip abduction moment, after excluding knees with the worst joint space grade at baseline (which could not progress).Results. The 57 participants (63% women) with mild to moderate OA had a mean age of 67 years and a mean body mass index of 29. A greater internal hip abduction moment during gait was associated with a reduced likelihood of medial tibiofemoral OA progression, with OR/unit hip abduction moment of 0.52 and a 95% confidence interval (95% CI) of 0.32-0.85. This protective effect persisted after adjustment for age, sex, walking speed, knee pain severity, physical activity, varus malalignment severity, hip OA presence, and hip OA symptom presence, with an adjusted OR of 0.43 a 95% CI of 0.22-0.81. Conclusion.A greater hip abduction moment during gait at baseline protected against ipsilateral medial OA progression from baseline to 18 months. The likelihood of medial tibiofemoral OA progression was reduced 50% per 1 unit of hip abduction moment.