Bilateral discoid medial meniscus associated with meniscal tears and hypoplasia of the medial femoral condyle

RATIONALE Bilateral discoid medial menisci is an extremely rare abnormality of the knee joint. The presence of a discoid medial meniscus has been associated with magnetic resonance imaging (MRI) and radiographic changes in the tibial region, such as cupping of the medial tibial plateau and tibial physis collapse. While discoid medial meniscal tears with hypoplasia of the femoral medial condyles have not been previously reported. Herein, we report a case of bilateral discoid medial menisci associated with meniscal tears and femoral bone changes. PATIENT CONCERNS A 28-year-old man presented with left knee pain and restricted range of motion; the right knee was asymptomatic. DIAGNOSES Based on radiographic and MRI findings, he was diagnosed with bilateral discoid medial meniscal tears. INTERVENTIONS Partial meniscectomy and reshaping were performed for the torn discoid medial meniscus of the left knee only. OUTCOMES MRI revealed short, flattened femoral medial condyles in the coronal and sagittal planes, and hypoplasia of the femoral medial condyles in the axial plane; these findings were confirmed arthroscopically in the left knee. The patient had a satisfactory results at the 12-month follow-up. LESSONS This case indicates a potential link between discoid medial menisci and hypoplasia of the femoral medial condyle. We recommend preservation of the discoid medial meniscus in asymptomatic patients, while arthroscopic partial meniscectomy and reshaping is recommended in symptomatic patients.