Association between medial meniscal extrusion and knee structural progression in adults with symptomatic knee osteoarthritis — a prospective cohort study

Objective: To examine the association between medial meniscal extrusion and structural progression in adults with symptomatic knee osteoarthritis (OA). Methods: This prospective cohort study examined 176 participants with symptomatic knee OA recruited into a randomised controlled trial. The participants underwent magnetic resonance imaging (MRI) of the study knee at baseline and approximately 2 years later. Meniscal extrusion, tibial cartilage volume, and tibiofemoral bone marrow lesions (BMLs) were measured from MRI using validated methods. Results: Participants with medial meniscal extrusion ≥ 3 mm had a higher prevalence of lateral tibiofemoral BMLs at baseline (OR = 2.21, 95% CI 1.06–4.61, p = 0.035), and those with medial meniscal extrusion 2–3 mm had a higher likelihood of lateral BML worsening over 2 years (OR = 3.76, 95% CI 1.35–10.52, p = 0.011), compared with those with medial meniscal extrusion < 2 mm. Participants with stable medial meniscal extrusion had a lower likelihood of lateral BML worsening compared with those with regression of medial meniscal extrusion over 2 years (OR = 0.20, 95% CI 0.07–0.56, p = 0.002). There were no associations between medial meniscal extrusion and tibial cartilage volume or medial tibiofemoral BMLs. Conclusions: Our study showed associations between medial meniscal extrusion and baseline prevalence and worsening over 2 years of lateral tibiofemoral BMLs in people with symptomatic knee OA. Although the reasons for the lack of associations in the medial compartment are not clear, our results suggest a role of medial meniscal extrusion in predicting structural progression in lateral knee OA and that meniscal extrusion might be a potential target in the management of knee OA.