Symptomatic Complete Discoid Medial Meniscus Completely Coalesced With the Anterior Cruciate Ligament: a Case Report

Rationale: Complete discoid medial meniscus is an extremely rare abnormality of the knee joint whose meniscus has a discoid shape rather than a normal semilunar one. Several medial meniscus anomalies including anomalous insertion have been reported in the literature. This report presents a rare case of symptomatic complete discoid medial meniscus whose anterolateral (apical) portion was completely coalesced with the ACL. MRI, radiographic and arthroscopic findings in the medial compartment are to be submitted.Patient concerns and diagnoses: A 29-year-old male presented with intermittent pain and swelling of the right knee for 2 years. Based on radiographic, MRI and physical examination findings, he was diagnosed with discoid medial meniscus tears. Interventions and outcomes: Arthroscopic saucerization were performed for the torn discoid medial meniscus of the right knee. Arthroscopic examination revealed a complete discoid medial meniscus and the anterolateral (apical) portion of which was completely coalesced with the ACL. Careful Probing of the meniscal surface revealed there was a longitudinal tear extending from the tibial spine to the midportion of the meniscus. Arthroscopic saucerization of the discoid meniscus were performed After closely cutting the meniscus around the ACL. The patient reported a satisfactory results at the 12-month follow-up.Lessons: Complete discoid medial meniscus is an extremely rare abnormality, and this case presents the third complete discoid medial meniscus whose anterolateral (apical) portion was completely coalesced with the ACL. The current case we present strongly supports the theory that ACL and meniscus were differentiated from the same mesenchyme.