This is, to our knowledge, the first demonstration that in primary knee OA varus alignment increases risk of medial OA progression, that valgus alignment increases risk of lateral OA progression, that burden of malalignment predicts decline in physical function, and that these effects can be detected after as little as 18 months of observation.

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.

Objective-Varus and valgus alignment increase, respectively, medial and lateral tibiofemoral load. Alignment was associated with tibiofemoral osteoarthritis progression in previous studies; an effect on risk of incident osteoarthritis is less certain. We tested whether alignment influences the risk of incident and progressive radiographic tibiofemoral osteoarthritis.Methods-In an observational, longitudinal study of the MOST (Multicenter Osteoarthritis Study) cohort, full-limb x-rays to measure alignment were acquired at baseline and knee x-rays were acquired at baseline and 30 months. Varus alignment was defined as ≤ 178° and valgus as ≥ 182°. Using logistic regression and GEE, we examined the association of baseline alignment and incident osteoarthritis at 30 months (in knees without osteoarthritis at baseline), and alignment and osteoarthritis progression (in knees with baseline osteoarthritis). All analyses were adjusted for age, gender, BMI, knee injury, laxity, and extensor strength, with neutral knees as referent.Results-2958 knees (1752 participants) were without osteoarthritis at baseline. Varus (adj. OR 1.49, 95% CI 1.06, 2.10) but not valgus alignment was associated with incident osteoarthritis. 1307 knees (950 participants) had osteoarthritis at baseline. Varus alignment was associated with a greater risk of medial osteoarthritis progression (adj. OR 3.59, 95% CI 2.62, 4.92) and a reduced risk of lateral progression, and valgus with a greater risk of lateral progression (adj. OR 4.85, 95% CI 3.17, 7.42) and a reduced risk of medial progression.Conclusion-Varus but not valgus alignment increased the risk of incident tibiofemoral osteoarthritis. In knees with osteoarthritis, varus and valgus alignment each increased the risk of progression in the biomechanically stressed compartment and reduced the risk of progression in the unloaded compartment.