MRI-defined Osteophyte Presence and Concomitant Cartilage Damage in Knees with Incident Tibiofemoral Osteoarthritis: Data From The Pivotal Osteoarthritis Initiative Magnetic Resonance Imaging Analyses (POMA) Study.

OBJECTIVE To describe compartmental frequencies of MRI-defined osteophytes and co-localized cartilage damage and evaluate the associations of osteophyte (OP) size with any ipsicompartmental cartilage damage in knees with incident tibiofemoral radiographic knee osteoarthritis (ROA). METHODS We evaluated knees from the Osteoarthritis Initiative without ROA at baseline that developed ROA during a 4-year interval. Semi-quantitative MRI scoring of osteophytes and cartilage damage was performed at the time point when ROA was diagnosed, defined as Kellgren-Lawrence grade ≥ 2, using the MOAKS instrument. The frequencies of maximum osteophyte size and maximum grade of ipsicompartmental (i.e., patellofemoral, medial tibiofemoral, lateral tibiofemoral, posterior femur) cartilage damage were assessed. Generalized estimating equations were used to determine the association of MRI-defined maximum osteophyte size with presence of any (excluding focal superficial defects) ipsicompartmental cartilage damage. RESULTS 296 knees that did not have tibiofemoral ROA at the baseline visit but developed ROA during the 48- month observational period were included. In the patellofemoral, medial tibiofemoral and lateral tibiofemoral compartments, the most frequent OP grade was 1 (67.6%, 59.1% and 51.7%, respectively), and in the posterior femur it was 0 (51.7%). For all compartments except the posterior femur, a linear trend was found between increasing maximum OP size and the presence of any concomitant cartilage damage. CONCLUSIONS In this sample of knees with incident tibiofemoral ROA, the patellofemoral joint showed more severe cartilage damage than other compartments regardless of concomitant osteophyte size. In the posterior femur, cartilage damage was rare despite the presence or size of concomitant osteophytes.