A rare case of posterolateral dislocation of the lateral discoid meniscus associated with an osteochondral lesion of the medial femoral condyle

Discoid meniscus (DM) is a congenital anatomical variant that predisposes adolescents to meniscal injury, most commonly involving the lateral meniscus. Osteochondral lesions of the knee, including osteochondritis dissecans (OCD) and acute osteochondral fractures (AOF) may be associated with DM of the same compartment of the knee. We report a unique case of a 14-year-old boy with a post-traumatic dislocation of the lateral DM and an osteochondral lesion of the medial femoral condyle demonstrated with radiographs, computed tomography (CT) and magnetic resonance imaging (MRI). The medial osteochondral lesion was well-demarcated, had regular margins and minimal bone marrow oedema favouring OCD over AOF. A conservative approach was adopted for the osteochondral lesion, while surgical treatment was performed for the meniscal pathology. Follow-up MRI at two months showed almost complete resolution of the osteochondral lesion. This case raises questions regarding relationship between meniscal abnormalities and osteochondral lesions and highlights the complexity of the osteochondral lesions during skeletal growth. Further studies are needed to clarify whether this association represents a coincidental finding or a clinically relevant relationship.