Comparison of meniscal extrusion and osteophyte formation at the intercondylar notch as a predictive biomarker for incidence of knee osteoarthritis-Data from the Osteoarthritis Initiative-

Background: Medial meniscal extrusion (ME) is a biomarker to predict later development of knee osteoarthritis (KOA). On the other hand, we have reported osteophyte formation at the posterior condylar notch of the femur served as a biomarker for the same purpose. The purpose of this study is to compare capacity of the two biomarkers in predicting KOA development. Methods: Two cohort of knees were established utilizing publicly available data from the Osteoarthritis Initiative (OAI). No OA group (NOA) consisted of knees that were grade 0 or 1 on Kellgren and Lawrence grade (K/L) both at baseline and 48 months later, and pre-radiographic-OA group (PROA) consisted of knees that were grade 0 or 1 at baseline but grade ≥2 48 months later. Baseline MR images were evaluated in terms of ME and osteophyte formation at the posterior condylar notch. ME was evaluated both by meniscus subluxation index (MSI) indicating the ratio of the extruded width of the medial meniscus to the width of medial meniscal body and by the medial radial displacement (MRD) indicating actual extruded width. The size of the osteophyte was assessed using a semi-quantitative whole-organ magnetic resonance imaging score (WORMS). The predictive accuracy of KOA was assessed by the area under the receiver operating characteristic curve (AUC) and optimal cutoff was determined for each parameter. Results: The AUC for MSI was 0.654 (0.561–0.748: 95% CI) and the cutoff value was determined as 17%. That for MRD was 0.677 (0.584–0.770) and the cutoff value was 2.2 mm. The AUC for the WORMS score at the posterior condylar notch was 0.667 (0.579–0.756) and the cutoff value was 2. Conclusions: Similar predicting capacity of KOA development was found both in ME and osteophyte formation at the posterior condylar notch. Using these simple parameter, mas-screening for KOA development would be possible.