Medial femoral condyle OCD (osteochondritis dissecans): correlation between imaging and arthroscopy.

Osteochondritis dissecans (OCD) describes a pathologic condition centered at the osteochondral junction that may result in an unstable subchondral fragment (progeny), disruption of the overlying cartilage, which may separate from the underlying parent bone. It is one of the causes of chronic knee pain in children and young adults. The current literature on OCD lesions focuses primarily on the medial femoral condyle (MFC), but inconsistent use of terminology, particularly in the distinction of OCD lesions between skeletally immature and mature patients has created uncertainty regarding imaging workup, treatment, and long-term prognosis. This article reviews the pathophysiology of MFC OCD lesions, highlighting the role of endochondral ossification at the secondary growth plate of the immature femoral condyles, the rationale behind the imaging work-up, and key imaging findings that can distinguish between stable lesions, unstable lesions, and physiologic variants. This overview also provides a case-based review to introduce imaging correlates with the ROCK (Research in Osteochondritis of the Knee) arthroscopic classification.