Juvenile Knee Osteochondritis Dissecans.

Osteochondritis dissecans (OCD) is defined as "a focal, idiopathic alteration of subchondral bone with risk for instability and disruption of adjacent articular cartilage that may result in premature osteoarthritis." Hypotheses regarding the etiology of OCD include ischemia, repetitive trauma, accessory centers of ossification, and genetic factors. OCD may present in any joint and throughout the articular surface but most commonly presents at the lateral aspect of the medial femoral condyle. Knee pain is the most commonly presenting symptom, and nearly one-third of patients present with bilateral lesions. Clinical and radiographic markers of stability (or instability) commonly dictate initial treatment. Risk factors for lesion instability include those related to the clinical presentation (i.e., chronologic age ≥14 years, effusion on physical examination, and any loss of range of motion). Preliminary imaging should include bilateral radiographs (anteroposterior, tunnel, lateral, and patella view) and an assessment of alignment. Magnetic resonance imaging is the advanced imaging of choice because of its ability to assess for lesion instability, primarily defined by the presence of an articular breach. For stable OCD lesions, nonoperative management with activity and temporary weight-bearing restrictions (with or without a brace) is often successful-favoring younger patients (aged < 12 years or with open physes) and smaller lesions in non-weight-bearing locations (far medial/lateral or posterior). Surgical management is reserved for patients in whom nonsurgical treatment fails, who have a high risk of failure, or who present with an unstable lesion. Surgical treatment of stable lesions includes retroarticular or transarticular drilling. Unstable lesions, if repairable, are treated with drilling and fixation with or without grafts. Some lesions are not amenable to fixation and thus warrant either cell-based (autologous chondrocyte implantation) or structural-based (osteochondral autograft or allograft) cartilage treatments. Return-to-sport rates are high (>85%) in skeletally immature knee OCD patients, regardless of treatment.