Ultrasonographic evaluation of medial radial displacement of the medial meniscus in knee osteoarthritis

Objective To evaluate medial radial displacement (MRD) of the medial meniscus in osteoarthritic (OA) and normal knees, with and without weight bearing, using ultrasonography (US), and to prospectively evaluate the time course of changes in MRD in OA knees. Methods. The study subjects were 78 patients with OA of the knee (69% female; mean age 66.4 years) and 20 healthy, asymptomatic subjects (70% female; mean age 64.5 years) who served as a control group. The OA stage was determined according to the Kellgren/Lawrence (K/ L) radiographic grading system. US measurement of MRD was performed with subjects in the supine and standing positions. With the exception of subjects who dropped out, 58 OA knees (followup rate 74%) were evaluated at baseline and similar to 1 year later. Results. The medial meniscus was significantly displaced radially by weight bearing in control knees (P < 0.001) and in knees with K/ L grades 1-3 OA (P < 0.01 for each comparison). MRD in either the supine or the standing position was not significantly different between the control knees and the K/L grade 1 knees, but significant differences were noted between the control knees and K/ L grade 2 or more severe OA knees (P < 0.01 for each comparison). MRD of the medial meniscus had increased significantly on followup in all knees (P < 0.05 for each comparison) excluding K/ L grade 4 knees in the standing position. Conclusion. MRD of the medial meniscus increased with weight bearing and during followup. These findings suggest a close association between extraarticular displacement of the medial meniscus and progression of OA.