Bilateral Occurrence and Morphologic Analysis of Complete Discoid Lateral Meniscus

PURPOSE The aim of the study was to investigate and analyze bilateral incidence and morphology of complete discoid lateral meniscus (DLM) with possible relation to tears and symptoms in knee joints. MATERIALS AND METHODS Thirty-eight consecutive patients with symptomatic or already-torn complete DLM on magnetic resonance imaging in a unilateral knee underwent diagnostic arthroscopy on both knee joints upon agreement. The presence and shape of complete DLM as well as presence and pattern of tear were recorded accordingly. RESULTS In total, 89.5% (34 of 38 patients) showed bilateral complete DLM, and 84.2% yielded bilateralism with identical shape. Cape-slab was the most frequent shape, comprising 68.8% of patients with identically-shaped bilateral DLM overall. Tear patterns were more frequent, in the order of longitudinal, simple horizontal, radial, and degenerative; however, the morphological shape of complete DLM was not significantly related to tear incidence or pattern. Meniscus tears and knee symptoms occurred in the contralateral knee with incidences of 32.4% and 26.5% in patients with bilateral complete DLM, respectively. CONCLUSION Based on these findings, more aggressive warning on the presence of discoid pathology and the need for evaluation on the contralateral knee should be considered during consultation with patients with symptomatic complete DLM in a unilateral knee in the outpatient clinic.