Osteochondritis Dissecans

Overview

Definition

Osteochondritis dissecans (OCD) is a disorder characterized by aseptic necrosis of subchondral bone that results in focal detachment and displacement of bone and cartilage into the joint space. The term osteochondritis is a misnomer, as histologic analysis reveals a lack of inflammatory cells.

Epidemiology

• Prevalence: 15–29 per 100,000 patients
• Peak age: 12–19 years
• Male > female
• Higher incidence in young athletes

Etiology and Pathophysiology

Etiology

The exact etiology is unknown. Many theories have been proposed, and OCD is likely multifactorial.

• Trauma: 
  • Repetitive microtrauma (mechanical stress from competitive sports)
  • Direct trauma (isolated injury)
• Ischemia
• Genetic predisposition

Pathophysiology

Pathogenesis of osteochondritis dissecans:

• Repetitive microtrauma → injury to the subchondral bone → fragmentation
• A defect develops between the osteochondral lesion and the underlying bone.
• Results in hypovascularity → osteonecrosis of the lesion
• Involvement of the overlying cartilage → instability of the fragment
• Subchondral bone and cartilage may become partially or totally separated.

Stages of progression in osteochondritis dissecans:

• Stage I: small area of compression of the subchondral bone
• Stage II: partial detachment of an osteochondral fragment
• Stage III: 
  • Complete detachment of a fragment
  • Remains within the underlying crater bed
• Stage IV: 
  • Complete detachment of a fragment
  • Displaced from crater bed (loose body)

Clinical Presentation

Symptoms

Some patients may be asymptomatic, with OCD found incidentally on imaging. However, symptomatic individuals may experience:

• Chronic pain in the affected joint: 
  • Increases with activity
  • Alleviated at rest
• Progressive symptoms, such as:
  • Joint stiffness
  • Intermittent swelling
  • Joint locking or catching (may signal a loose body)
  • Joint instability
• Most commonly affected joints:
  • Knee (75% of cases)
  • Elbow (6% of cases)
  • Ankle (4% of cases)

Physical examination

• Localized tenderness to palpation at the site of the lesion, particularly:
  • Medial femoral condyle of the knee
  • Radiocapitellar joint of the elbow
  • Tibiotalar joint of the ankle
• Painful range of motion
• Range of motion:
  • Usually normal if the knee is affected
  • Often diminished in an affected elbow
• Joint effusion
• Crepitus
• Wilson’s test: 
  • Pain with knee extension and internal rotation
  • Has been described with OCD, but lacks sensitivity
• Abnormal gait:
  • May be seen in some patients with knee involvement
  • Affected leg is externally rotated with ambulation.

Diagnosis

A diagnosis of OCD should be suspected in adolescents with a characteristic presentation of joint pain and involvement in repetitive activities and sports.

X-ray

X-rays of the affected joint are usually diagnostic and are the initial testing method of choice. However, these images can be normal in the early disease stages.

Knee:

• Findings:
  • Subcortical, crescent-shaped lucency is often first detected.
  • Subchondral bony fragment
• Frequent lesion locations:
  • Medial condyle (77%)
  • Lateral condyle (17%)
  • Patella (7%)

Elbow:

• Lateral capitellum flattening
• Subchondral sclerosis
• Fragmentation of the capitellum

Ankle:

• Normal in ⅓ of cases
• Cup-shaped lesion on the talus

MRI

• Should be considered in symptomatic patients with normal X-rays
• More sensitive in detecting subchondral changes and can be used in staging
• Gadolinium can be used to evaluate the blood supply to the area.
• Frequently used in preoperative planning

Management

The main goal of management is to achieve healing of the osteochondral lesion and return the affected joint to full function. Specialty referrals for sports medicine or orthopedic surgery may be needed.

Conservative management

• Limit weight-bearing and activity:
  • Critically important to prevent progression
  • Return to activity may occur when: 
    • Pain-free
    • Active full range of motion improves
    • Evidence of healing
• Joint immobilization
• Physical therapy
• Indications for conservative management:
  • Skeletally immature patients with open physes and without an intra-articular foreign body
  • Adult patients who have a small, stable, asymptomatic fragment
• Asymptomatic patients with incidental X-ray findings of osteochondral lesions: 
  • Repeat X-rays every 6 months.
  • Follow the patient until skeletal maturity or until the lesion has healed.

Surgical management

• Indications:
  • Signs of joint instability
  • Expanding lesion on x-rays
  • Failed nonoperative treatment
  • Intra-articular loose body
• Techniques:
  • Arthroscopic subchondral drilling 
  • Fixation of unstable lesion
  • Arthroscopic excision, curettage, and drilling
  • Autologous chondral transplantation 
• Choice depends on skeletal maturity, stage of the disease, and size of the lesion.

Prognosis

• Most patients with stable lesions will have spontaneous healing with conservative measures.
• Success rates for unstable lesions varies depending on the severity and surgical technique: 30%–100%
• Patients have an increased risk of developing osteoarthritis of the joint.
• Factors linked with an improved prognosis:
  • Younger age
  • Intact articular cartilage
  • Smaller osteochondral lesions
  • Stable lesions

Differential Diagnosis

• Meniscal tear: an acute injury often seen in younger patients: The presentation may include a tearing or popping sensation during the injury, knee pain, decreased range of motion, locking or catching, and joint effusion. The diagnosis is based on the physical examination and imaging. Management includes conservative measures and surgery for severe injury.
• Plica syndrome: irritation and inflammation of the medial synovial component of the knee, which can occur with repetitive trauma: Patients may experience knee pain, often of the medial aspect of the joint, with a catching or popping sensation. A definitive diagnosis is provided by arthroscopy. Management consists of conservative measures, physical therapy, intra-articular steroid injections, and arthroscopic surgery for refractory cases.
• Patellofemoral syndrome: most common cause of anterior knee pain, which may result from malalignment of the leg, muscular imbalance, overactivity, or trauma: Patellofemoral syndrome produces dull and generalized anterior knee pain that is exacerbated by activity or prolonged sitting. Patellofemoral syndrome is a diagnosis of exclusion, and other intra-articular etiologies should be ruled out. Conservative measures and physical therapy are used in management.
• Little League elbow: overuse injury that results in apophysitis of the medial epicondyle of the elbow: This condition is often associated with repetitive throwing, commonly in preadolescent and adolescent baseball pitchers. Patients develop elbow pain, particularly of the medial epicondyle. The diagnosis is clinical, and management includes conservative measures and physical therapy.
• Panner disease: osteochondrosis of the humeral capitellum epiphysis consisting of atypical ossification, necrosis, and regeneration: In contrast to OCD, this disorder is seen at younger ages and does not progress to a loose body. Patients present with elbow pain, stiffness, and limited range of motion. The diagnosis is made with imaging, and management includes conservative measures.
• Medial epicondylitis: also known as “golfer’s elbow”: This disorder is caused by valgus force on the elbow resulting in inflammation of the wrist flexor group tendon at its insertion on the medial epicondyle. Patients will have medial elbow pain and tenderness. Pain will be provoked by flexion of the wrist and pronation against resistance. The diagnosis is clinical, and management involves conservative measures and physical therapy.
• Lateral epicondylitis: also known as “tennis elbow”: This condition results from inflammation of the extensor tendons of the forearm at their insertion on the lateral epicondyle. Patients will have lateral elbow pain that can radiate to the forearm. Pain will be provoked by wrist extension with resistance. The diagnosis is clinical, and management involves conservative measures and physical therapy.
• Ankle sprain: injury of the ankle, most often from inversion of the foot: Patients will have pain, tenderness, and swelling of the anterolateral ankle (most common location). The diagnosis is clinical. Imaging may be done to exclude other causes of ankle pain. Management includes conservative measures and physical therapy.