Medial compartment defects progress at a more rapid rate than lateral cartilage defects in older adults with minimal to moderate knee osteoarthritis (OA): data from the OA initiative

Purpose To determine: (1) rates and risk factors for progression of lateral and medial full-thickness cartilage defect size in older adults without severe knee osteoarthritis (OA), and (2) whether risk factors for defect progression differ for knees with Kellgren–Lawrence OA grade 3 (moderate) OA versus grades 0–2 (none to mild) OA. Methods Three-hundred and eighty adults enrolled in the Osteoarthritis Initiative were included (43% male, mean age 63.0 SD 9.2 years). Ethical approval was obtained at all study sites prior to enrollment. All participants had full-thickness tibial or weight-bearing femoral condylar cartilage defects on baseline knee MRIs. Baseline OA grade was KL grade 3 in 71.3% and grades 0–2 in 21.7% of participants. Repeat MRIs were obtained at a minimum 2-year follow-up. Independent risk of progression in defect size due to demographic factors, knee alignment, OA grade, knee injury and surgery history, and baseline knee symptoms was determined by multivariate Cox proportional hazards and linear regression modeling. Results The average increase in defect size over 2 years for lateral defects was 0.18 cm 2 (SD 0.60) and for medial defects was 0.49 cm 2 (SD 1.09). Independent predictors of medical defect size progression were bipolar defects (beta 0.47 SE 0.08; p