Description

• Osteochondritis dissecans (OCD) is a lesion of subchondral bone that may cause separation from and instability of overlying articular cartilage.
• The loose piece of bone and cartilage may migrate into the joint causing instability, pain, or locking.
• It is the most common cause of an intra-articular loose body in adolescents.
• The knee is the most commonly affected joint.
• OCD can occur in any diarthrodial joint, including the following in decreasing order of frequency:
  • Elbow (capitellum)
  • Ankle (talar dome or tibial plafond)
  • Tarsal navicular
  • Hip (femoral capital epiphysis)
  • Shoulder (humeral head or glenoid)
  • Wrist (scaphoid)
• System(s) affected: musculoskeletal

Epidemiology

Incidence

• Unknown: estimated 2 to 5:10,000 persons
• Predominant age: 10 to 40 years
• Juvenile type (juvenile OCD) in children and adolescents prior to physeal closure
• Predominant sex: male > female (2:1). Female incidence is increasing (1).

Etiology and Pathophysiology

• Loss of subchondral bone support leads to degenerative cartilage changes: softening and fibromatous fissuring.
• A fragment may detach and become a loose body within the affected joint.
• Primary insult in OCD is to the underlying bone with secondary cartilage damage due to focal bony necrosis. Cartilage is avascular and heals through the vascular supply of the underlying bone, which stimulates inflammation, repair, and remodeling.
• Difficult to predict which lesions heal
• Precise etiology is unclear; theories include:
  • Trauma or repetitive microtrauma
  • Ischemia
  • Familial predisposition
  • Fragile blood supply of the physeal line
  • Epiphyseal abnormalities
  • Endocrine imbalance
• The most popular current theory is repetitive microtrauma with resultant vascular insufficiency.
• Most commonly affected joints are:
  • Knee: overuse and with patellar dislocation and injury to the anterior cruciate ligament; bilateral involvement noted in up to 30% of patients
  • Elbow: overuse injury in overhead throwers and racquet sports as well as gymnasts
  • Ankle: frequently associated with history of previous ankle sprain
• Relationship between adult (physeal closure) and juvenile (physeal open) forms of OCD is unclear.
• Juvenile OCD is more likely to heal spontaneously compared to adult OCD (2).

Genetics
Emerging evidence of aggrecan (ACAN) gene connection (3). Rare case reports of bilateral involvement in twins exist.

Risk Factors

• Trauma
• High physical activity level (children and adults)
• Participating in multiple sports, especially gymnastics and overhead sports
• Abnormal mechanical axis of the leg
  • Varus axis and medial condyle OCD
  • Valgus axis and lateral condyle OCD

Pediatric Considerations
Although still idiopathic, the mean age in juvenile OCD is decreasing, and the prevalence in girls is increasing with changes in childhood sports participation (1).

General Prevention

There is no demonstrated way to avoid developing OCD.