s / Osteoarthritis and Cartilage 20 (2012) S54–S296 S213 those with medial JSN (Table 1), and OV1 was significantly greater in knees with lateral than medial JSN1 in the FLASH sample (p1⁄40.001). Conclusions: Lateral uni-compartmental JSN is a strong predictor of cartilage loss in the lateral (but notmedial) femorotibial compartment, and medial uni-compartmental JSN is a strong predictor of cartilage loss in the medial (but not lateral) femorotibial compartment. The rate of lateral cartilage thickness loss in knees with lateral JSN was at least as great as that of medial cartilage loss in knees with the same medial JSN grade. This makes it attractive to enrich OA study populations with knees displaying lateral JSN, also in view of greater generalizability of results and potential treatment effects. In mixed cohorts with medial and lateral JSN, OV1 represents a uniform endpoint that can capture rates of change independent of the location. 424 ASSOCIATION OF FREQUENT KNEE BENDING ACTIVITY WITH FOCAL KNEE LESIONS DETECTED WITH 3T MRI OVER A PERIOD OF 3 YEARSDATA FROM THE OSTEOARTHRITIS INITIATIVE H. Alizai , W. Virayavanich , W. Lin , L. Nardo , M.C. Nevitt , J.A. Lynch , C.E. McCulloch , T.M. Link . Univ. of CaliforniaSan Francisco, San Francisco, CA, USA; Ramathibodi Hosp., Mahidol Univ., Bangkok, Thailand Purpose: To evaluate the association of frequent knee bending activities with the prevalence and progression of cartilage and meniscal abnormalities over a period of 3 years assessed with 3 Tesla (3T) MRI and to determine the effect of frequent knee bending on the different compartments of the knee. Materials and Methods: We recruited 115 subjects without radiographic knee osteoarthritis (OA) but with risk factors for OA from the Osteoarthritis Initiative (OAI) database. The inclusion criteria were: (1) age 45-55 years old, (2) body mass index (BMI) of 19-27 kg/m2, (3) Western Ontario and McMaster University (WOMAC) pain score of zero at baseline. Cartilage and meniscal abnormalities were graded on 3T MRI studies using the Whole-Organ MRI Score (WORMS). A self-reported questionnaire of knee bending activities (kneeling, squatting, stair climbing, and weight lifting) was completed at the initial visit. Logistic regression was used to determine the association of frequent knee bending activity with cartilage and meniscal abnormalities and odds ratios (OR) were calculated. Results: Frequent knee bending activities were associated with an increased risk of prevalent cartilage lesions (OR 3.63, 95%CI 1.39-9.52), in particular in the patellofemoral compartment (OR 3.09, 95%CI 1.22-7.79). The increase in risk associated with frequent knee bending was higher in subjects involved in two or more knee bending activities. At 3-year followup, individuals with frequent knee bending activities had higher progression of cartilage (OR 4.12, 95%CI 1.27-13.36) and meniscal abnormalities (OR 4.34, 95%CI 1.16-16.32). Conclusion: Frequent knee bending activities were associated with higher prevalence and progression of knee cartilage lesions in asymptomatic middle-aged subject, in particular at the patellofemoral compartment.