Osteochondritis Dissecans of the Knee

Excerpt

Osteochondritis dissecans of the knee is a relatively rare condition, categorized as a form of osteonecrosis affecting the subchondral bone. The condition tends to manifest as knee dysfunction and pain, predominantly affecting school-aged children and adolescents. More specifically, in osteochondritis dissecans, a piece of the subchondral bone and articular cartilage detaches from the underlying bone. The ensuing fragment may be either stable, indicating intact overlying articular cartilage, or unstable, which has significant prognostic implications. Osteochondritis dissecans is more prevalent in individuals aged 10 to 20, with a higher incidence in males than females. Juvenile osteochondritis dissecans occurs in patients with open growth plates or physes, whereas adult osteochondritis dissecans applies to skeletally mature patients.

Although osteochondritis dissecans has been recognized for over a century, its exact cause of knee dysfunction and pain remains unclear. Recently, the Research in Osteochondritis Dissecans of the Knee (ROCK) study group summarized the currently recognized pathophysiology of osteochondritis dissecans as an acquired subchondral lesion characterized by osseous resorption, collapse, and sequestrum formation. König originally proposed the concept in 1887, suggesting an inflammatory etiology as a contributing factor in osteochondritis dissecans development. Despite the lack of evidence of an inflammatory component in histopathology, the term "osteochondritis" has persisted over the years.

Individuals with this condition may either present with knee pain as a primary complaint or incidentally discover the findings during radiographs conducted for unrelated injuries. Clinicians typically rely on plain radiographs to diagnose and identify the condition, with magnetic resonance imaging (MRI) as the primary staging tool. The typical location for these lesions is the distal femur, especially in the lateral aspect of the medial femoral condyle. Initial treatment for stable lesions includes rest, nonsteroidal anti-inflammatory drugs, activity avoidance, and physical therapy. Skeletally immature patients often respond well to nonoperative treatment, whereas skeletally mature individuals with large lesions or the formation of intraarticular loose bodies may require surgical intervention. The most important prognostic factor involves the patient's skeletal age at the time of symptom onset. Although over 50% of children with osteochondritis dissecans typically recover through conservative measures within 6 to 18 months, adults often necessitate surgical intervention. If the condition is left untreated, affected patients may experience degenerative changes, chronic pain, and mechanical symptoms such as locking and clicking.