Overview
Definition:
Osteochondritis dissecans (OCD) is a joint condition where a piece of bone and its overlying cartilage separates from the end of the bone, typically due to a lack of blood supply
In the knee, it most commonly affects the medial femoral condyle, followed by the lateral femoral condyle and patella
The separated fragment may remain in place, displace into the joint, or become a loose body.
Epidemiology:
OCD of the knee is most prevalent in skeletally immature individuals, typically between the ages of 10 and 20 years
It is more common in males than females, with a male-to-female ratio of approximately 2:1 to 4:1
Bilateral involvement occurs in about 10-40% of cases
Sports participation is a significant risk factor.
Clinical Significance:
OCD of the knee is crucial to diagnose and manage promptly to prevent long-term sequelae such as osteoarthritis, joint instability, and chronic pain
Early and appropriate intervention can significantly improve functional outcomes and reduce the risk of degenerative joint disease.
Clinical Presentation
Symptoms:
Vague, activity-related knee pain, often localized to the medial or lateral joint line
Intermittent effusion or swelling
Clicking, catching, or locking sensation within the joint, especially with flexion or extension
Stiffness or reduced range of motion
Limp or antalgic gait
In some cases, asymptomatic incidental findings on imaging.
Signs:
Tenderness over the affected condyle or patella
Palpable effusion
Guarding and limited range of motion
Positive Wilson's test (pain and apprehension when the knee is flexed to 90 degrees and the tibia is passively internally rotated, followed by extension)
Crepitus may be present.
Diagnostic Criteria:
There are no strict universally applied diagnostic criteria beyond clinical suspicion and radiographic evidence
The staging of OCD lesions (e.g., Berndt and Hardy classification) is based on imaging findings and is crucial for management decisions.
Diagnostic Approach
History Taking:
Detailed history of knee pain onset and progression
Relationship of pain to activity and rest
Any history of trauma, repetitive stress, or previous knee injuries
Presence of mechanical symptoms like locking or catching
Family history of musculoskeletal disorders
Red flags include acute onset of severe pain, inability to bear weight, or signs of neurovascular compromise.
Physical Examination:
Observe gait and posture
Palpate for tenderness over the femoral condyles, patella, and joint lines
Assess range of motion, noting any limitations or crepitus
Perform specific tests such as Wilson's test, McMurray's test, and anterior/posterior drawer tests to rule out associated ligamentous injury
Examine the contralateral knee.
Investigations:
Plain radiographs: Anteroposterior (AP), lateral, and oblique views of the knee are essential
Standard view may miss subtle lesions
Weight-bearing AP views are important for evaluating joint stability
MRI: The gold standard for diagnosing OCD, providing detailed assessment of the fragment size, stability, extent of cartilage involvement, subchondral bone edema, and presence of loose bodies
It helps in classifying the lesion and guiding treatment
CT scan: Useful for assessing the bony architecture and for surgical planning in displaced fragments
Arthroscopy: Can be diagnostic and therapeutic, allowing direct visualization and intervention.
Differential Diagnosis:
Other causes of pediatric knee pain include Osgood-Schlatter disease, Sinding-Larsen-Johansson syndrome, patellofemoral pain syndrome, meniscal tears, osteochondral fractures, avascular necrosis, inflammatory arthropathies, and benign bone tumors
Distinguishing features often lie in the location of pain, specific physical findings, and characteristic imaging findings of OCD.
Management
Initial Management:
Activity modification: Rest, avoidance of high-impact activities
Non-steroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation control
Crutches for partial weight-bearing or non-weight-bearing as needed to relieve pain.
Medical Management:
Conservative management is the mainstay for stable lesions in skeletally immature patients
This involves a period of protected weight-bearing and gradual return to activity
Physical therapy to maintain range of motion and strength without stressing the lesion
Serial imaging to monitor healing and stability.
Surgical Management:
Surgical intervention is indicated for unstable lesions, displaced fragments, loose bodies, persistent symptoms despite conservative treatment, or in skeletally mature individuals
Options include: arthroscopic debridement and fixation (screws or pins) of the fragment, retrograde drilling of the fragment to promote vascularization, osteochondral autograft transplantation, or autologous chondrocyte implantation (ACI) for larger defects
Excision of the fragment and curettage of the defect may be performed for small, non-reconstructible fragments.
Supportive Care:
Pain management with appropriate analgesics
Post-operative rehabilitation protocols tailored to the surgical procedure
Education of the patient and family regarding the condition, treatment plan, and expected recovery
Nutritional support is generally not a primary concern unless there are co-existing conditions.
Complications
Early Complications:
Arthroscopy-related risks: infection, bleeding, nerve or blood vessel injury, chondral damage
Post-operative pain and swelling
Deep vein thrombosis (DVT).
Late Complications:
Progression to osteoarthritis due to loss of articular cartilage and joint surface incongruity
Chronic pain
Mechanical symptoms from loose bodies or unstable fragments
Non-union or malunion of the fragment
Stiffness and loss of range of motion
Development of secondary arthritis.
Prevention Strategies:
Early diagnosis and appropriate management based on lesion stability and skeletal maturity
Adherence to activity restrictions during conservative management
Meticulous surgical technique to ensure stable fixation and minimize cartilage damage
Aggressive rehabilitation to restore function and prevent stiffness.
Prognosis
Factors Affecting Prognosis:
Lesion size, location, and stability are the most critical factors
Skeletal maturity (younger patients generally have better healing potential)
Adherence to treatment protocols
Presence of associated injuries (e.g., meniscal tears)
Successful surgical intervention for unstable or displaced lesions.
Outcomes:
Good outcomes can be expected with timely and appropriate management, particularly for stable lesions in skeletally immature individuals treated conservatively
Surgical intervention for unstable lesions can restore joint congruity and function
However, some degree of long-term joint changes and potential for osteoarthritis remain a concern, especially with larger or neglected lesions.
Follow Up:
Regular follow-up with clinical assessment and serial imaging (radiographs or MRI) is crucial to monitor healing, assess stability, and detect any complications
The duration and frequency of follow-up depend on the treatment modality and individual progress, often extending for several years after initial treatment to monitor for long-term outcomes.
Key Points
Exam Focus:
Remember OCD commonly affects skeletally immature males, usually the medial femoral condyle
MRI is the investigation of choice for diagnosis and stability assessment
Stable lesions in children are managed conservatively with activity modification
unstable lesions and loose bodies require surgical intervention
Berndt and Hardy classification is key for staging.
Clinical Pearls:
Always consider OCD in a young athlete with persistent, activity-related knee pain, especially with mechanical symptoms
Wilson's test is a useful physical examination maneuver
Inquire about bilateral knee symptoms
Understand the difference in management based on skeletal maturity and lesion stability.
Common Mistakes:
Underestimating the significance of vague knee pain in pediatric patients
Failing to obtain adequate imaging (especially MRI) for suspected OCD
Inappropriately aggressive return to activity in conservatively managed cases
Misinterpreting the stability of OCD lesions on imaging, leading to delayed surgical intervention.