Medial Meniscus Extrusion During Weight-Bearing in Early-Stage Knee Osteoarthritis

To determine whether medial meniscus extrusion (MME) measured in the standing or supine position better characterizes early-stage knee osteoarthritis (OA) and to assess the association between MME in the optimal position and physical function.

This study included 43 community-dwelling women. MME was measured beneath the medial collateral ligament in the supine and standing positions. Early OA was defined by a Kellgren-Lawrence grade of 0-1, tenderness and/or stiffness around the knee, and a knee society score (KSS) symptom subscore ≤ 22. Thirteen participants were classified as having early OA, and 30 as asymptomatic. Firth logistic regression analysis was used to determine which MME measurement was more strongly associated with early OA. Multiple linear regression analysis was conducted to explore associations between the KSS function subscore and the MME in the predictive position.

MME standing was significantly greater in the early OA group than in the asymptomatic group (4.5 ± 1.2 mm vs. 3.1 ± 0.9 mm; p < 0.001; d = 1.3) and was independently associated with early knee OA (OR = 18.13 per 1 mm increase, 95%CI 1.88-323.91, p = 0.011). In regression models, MME standing was associated with self-reported knee function (β = - 0.31, p = 0.034), independently of quadriceps strength (β = 0.38, p = 0.004).

MME measured under weight-bearing conditions can help differentiate individuals with early knee OA from asymptomatic individuals with similar radiographic features and is associated with self-reported knee function, suggesting its potential as an adjunctive clinical indicator.