Osteochondritis dissecans is an acquired condition of uncertain, probably multifactorial, etiology that commonly affects the convex articular surface of a bone.1 Konig, who coined the phrase in 1888, believed that inflammation of the affected osteochondral tissue (osteochondritis), followed by necrosis, led to separation (Latin, dissecans) of the osteochondral fragment.2 Today it is more widely believed that the causative mechanism is chronic repetitive trauma, which is influenced by the mechanics and anatomy of the joint, bone, articular surface, and vascular distribution of the area involved. Other implicated factors include hereditary predisposition, defects of ossification, untreated acute trauma, and ischemia. It is thought that osteochondral injury or ischemia leads to weakening of the bone/cartilage interface that may heal spontaneously or may progress to osteochondral separation and a displaced free fragment (loose body) in the joint space. Age of presentation is variable, but most commonly is the 2nd and 3rd decades of life. Rarely, osteochondritis dissecans may occur in a patient younger than 10 years or older than 50 years of age. The incidence reportedly is increased in males and athletes. The standard presentation includes chronic joint pain and no antecedent trauma. Other reported symptoms include joint locking, catching, giving way, and swelling. Children have a better prognosis than adults and tend to heal with conservative management, whereas adults are more likely to require surgical intervention.