Role of full-thickness cartilage defects in knee osteoarthritis (OA) incidence and progression: Data from the OA Initiative.

The purpose of this study is to determine whether full-thickness tibiofemoral cartilage defects are predictive of incident radiographic OA, progression of radiographic OA, and progression to severe radiographic OA. Participants in the OA Initiative (n = 1317, 38.1% male, mean age 60.9 years SD 9.2) with baseline MRIs and Kellgren-Lawrence (KL) OA grade 0-3 (none to moderate OA) were included. All participants had follow-up radiographs at mean 4.9 years (max 8.0). The effect of full-thickness defect presence, size, and location on risk of incident OA (KL grade 2+), overall progression of OA (increase in KL grade 1+ points), or compartment-specific OA progression was assessed with Cox proportional hazards modeling with adjustment for demographic factors, weight, and knee alignment. The yearly incidence of tibiofemoral OA was 0.3% (CI 0.2-0.4%); defect presence, size, and location were not associated with incident OA risk. The yearly rate of OA progression was 3.8% in participants without tibiofemoral full-thickness defects, 6.7% with medial defects, and 6.3% with lateral defects. Medial bipolar (kissing) lesions were an independent risk factor for OA progression as well as medial compartment progression. Lateral tibial-sided full-thickness defects increased risk of lateral progression (increase in lateral OARSI grade). In older adults, isolated full-thickness cartilage defects do not increase short-term risk of incident OA. However, in the setting of preexisting mild or moderate OA, medial bipolar (kissing) defects increase risk of overall OA progression (KL grade) as well as progression of medial compartment OA. Lateral tibial defects increase risk of lateral compartment OA progression.