Although clinical reports have described medial meniscal subluxation (MMS) in knee OA, few controlled studies have used dynamic US to examine the potential impact of MMS on OA. The aim of this study was to assess MMS in patients with knee OA and in asymptomatic controls by US in different weight-bearing positions.
In a cross-sectional controlled study, MMS was evaluated by US in 33 symptomatic OA knees and in 13 control knees in supine neutral and unipodal weight-bearing positions. The reproducibility of US in this setting was assessed and the US measurements were compared between patients and controls.
MMS was observed more frequently in OA knees than in controls in the unipodal weight-bearing position both before (P = 0.014) and after (P = 0.035) walking 50 m. In both OA and control knees, an increase in MMS was observed in the unipodal weight-bearing positions compared with the supine neutral position, but this increase was greater in OA knees than in controls (P < 0.001).
Our findings confirm clinical observations that the medial meniscus undergoes significant subluxation in knee OA. The degree of subluxation is greater in weight-bearing than in non-weight-bearing positions. Dynamic US is a reproducible method for the assessment of MMS.