Medial Discoid Meniscus in a Pediatric Patient: A Case Report

The discoid meniscus is a congenital morphological variant characterized by an abnormally thickened, enlarged, and abnormally shaped meniscal structure.Although this condition predominantly involves the lateral meniscus, medial discoid meniscus represents a much less common presentation.The abnormal meniscal morphology may alter normal knee biomechanics and predispose the affected meniscus to instability, degeneration, and tearing.Clinical presentation is variable, as some patients remain asymptomatic, whereas others may develop pain, swelling, mechanical symptoms, or functional limitations, particularly in the presence of an associated meniscal tear.We present the case of a nine-year-old male with right knee pain, swelling, mechanical locking, and limited range of motion.Magnetic resonance imaging (MRI) demonstrated a complete medial discoid meniscus with a horizontal tear involving the body and posterior horn.The patient underwent knee arthroscopy that revealed a longitudinal meniscocapsular tear extending from the posterior third of the meniscal body to the posterior horn, with peripheral instability.Meniscocapsular repair was performed without initial remodeling.Although pain and function improved, a persistent flexion deformity subsequently required a second arthroscopy and meniscal remodeling.Following meniscal remodeling, the patient achieved full range of motion and remained pain-free and free of meniscal symptoms at six-month follow-up, with unrestricted return to sports activities.This case highlights the importance of recognizing meniscal variants and associated tears in pediatric patients with mechanical knee symptoms and supports addressing the abnormal discoid morphology during the initial surgical procedure, regardless of whether concomitant meniscal repair is required, to restore a more anatomical meniscal shape and potentially reduce the need for subsequent surgical intervention.