Discoid Lateral Meniscus Evaluation and Treatment

Abstract

Discoid lateral meniscus (DLM) is a variant of meniscal histomorphology that often presents in young, active pediatric populations. Patients may present with mechanical symptoms, joint line pain, swelling, and loss of motion especially with lack of terminal knee extension. DLM are prone to tearing, most frequently with horizontal patterns in children and complex patterns in adults. The PRiSM classification and assessment of DLM provide a comprehensive approach to evaluating DLMs arthroscopically, focusing on the following four factors: (1) meniscal width, (2) meniscal height, (3) stability, and (4) the presence of tearing. Meniscal width is defined as complete (Watanabe class I) or incomplete (Watanabe class II). Meniscal height is defined as normal or abnormal. DLMs may be stable, unstable posteriorly (Watanabe class III), unstable anteriorly, or unstable both anteriorly and posteriorly. After appropriate saucerization, the meniscus is carefully evaluated for the presence of a tear, and, if present, the tear type and location are noted. Multiple surgical tips may facilitate appropriate treatment of symptomatic DLMs. A more proximal and medial anteromedial portal should be created directed over the tibial spines into the lateral compartment for optimal working trajectory. Small joint and 70° scopes may also facilitate viewing in select cases. Switching portals frequently allows for a more complete assessment and treatment of DLMs. During the process of saucerization, the popliteal hiatus should be visualized, and this area is often thickened and enlarged which can contribute to meniscal instability. A variety of biters, shavers, and blades may be necessary for optimal saucerization. For unstable tears, traction sutures may facilitate controlling the DLM during saucerization. Once saucerization is complete, the presence of a tear should be thoroughly assessed. If possible, tears should be repaired, and surgeons should be prepared with a variety of repair techniques in addition to marrow stimulation or biologic augmentation to improve healing potential.