The Relationship between Lateral Femoral Condyle Morphology and the Risk for Lateral Discoid Meniscus Tears

Purpose: To evaluate whether the shape of lateral femoral condyle (LFC) affects the risk for tear in discoid lateral meniscus (DLM).

Background: Discoid lateral meniscus has increased risk for tears compared to normal meniscus, however it may be an incidental finding in MRI or knee arthroscopy. Previous studies has shown that knees with DLM have an unique morphology of LFC, it may be hypoplastic, flat or with cutoff sign. In the current study we evaluate the relationship between LFC shape and the risk of DLM tears.

Methods: We retrospectively reviewed our prospective database of knee arthroscopies for all consecutive cases with arthroscopy proven lateral discoid meniscus and retrievable knee MRI. The cases were divided into 2 cohorts: cohort (A) torn DLM, and (B) normal DLM. The coronal radius of LFC was measured using a mid-coronal T2-MRI image and using the geometrical basis for calculating circle radius based on 3 points. Demographic data was collected for both cohorts.

Results: Cohort A included 13 knees (12 patients) and cohort B included 17 knees (14 patients). The mean LFC radius in cohort A was , 22.7 mm (±3.3), significantly lower than the 32.8 mm (±3.7) mean LFC radius (p<.005). The mean age in cohort A was 22.4 years (±12.1), significantly lower than the 49.8 (±14.8) years mean age in cohort B (p < 0.005).

Conclusions: Coronally convex LFC (i.e. relatively small radius), increases the risk for DLM tears in young age compared to relatively flat LFC where DLM may stay normal in older patients.