Osteochondral Defect (OCD) & Osteochondritis Dissecans

An osteochondral defect (OCD) of the knee is damage to both the articular cartilage and the underlying subchondral bone. Fragments of cartilage and bone may remain stable within the joint, become partially detached, or break free entirely as loose bodies. Osteochondritis dissecans (OCD) is a specific and important subtype of osteochondral defect with distinct causes, a younger typical patient, and its own classification system.

Osteochondral defects share important overlap with other knee conditions — including Avascular Necrosis (AVN), which similarly involves subchondral bone injury, and Meniscus Tears, which frequently co-occur with cartilage damage. Ligament instability from an ACL Tear is also a recognized risk factor for developing focal cartilage defects.

Osteochondritis Dissecans (OCD)

Osteochondritis dissecans is a condition in which a segment of bone just beneath the articular cartilage loses its blood supply, causing that bone — and the cartilage above it — to gradually separate from the surrounding tissue. In the knee, the lateral surface of the medial femoral condyle is the most commonly affected site, though the lateral condyle and patella can also be involved.

Osteochondritis dissecans is most often diagnosed in children and adolescents between the ages of 10 and 20, particularly those who are active in sports. It is more common in males. The juvenile form — occurring before growth plates close — generally has a better prognosis than the adult form, as the developing skeleton retains a greater capacity for healing.

The condition exists on a spectrum from a stable lesion with intact overlying cartilage to a completely detached fragment (loose body) floating within the joint. Early detection and appropriate treatment are critical to preserving the joint surface and preventing the onset of early osteoarthritis.

Causes

1. Acute Trauma: A sudden injury or trauma to the knee, such as a sports-related injury (e.g., twisting, direct impact), can cause damage to the articular cartilage and underlying bone, leading to an osteochondral defect.

2. Repetitive Microtrauma: Activities that involve repetitive stress on the knee joint, such as running, jumping, or certain occupational activities, can gradually wear down the cartilage and bone. This is considered the primary mechanism in osteochondritis dissecans, where repeated microtrauma disrupts blood flow to the subchondral bone, triggering localized bone death (avascular necrosis) and eventual separation of the overlying cartilage.

3. Vascular Insufficiency: Disruption of the blood supply to the subchondral bone is central to the development of osteochondritis dissecans. Without adequate blood flow, the bone beneath the cartilage undergoes focal necrosis, weakening its structural support and allowing the overlying cartilage segment to become unstable.

4. Joint Instability: Conditions that cause instability in the knee joint, such as ligament injuries (e.g., ACL tears) or chronic knee laxity, can alter the normal biomechanics of the knee. This abnormal stress distribution can lead to focal areas of cartilage and bone damage.

5. Poor Joint Alignment: Malalignment of the knee joint, such as genu valgum (knock-knee) or genu varum (bow-leggedness), can increase the risk of developing osteochondral defects due to abnormal loading on specific areas of the joint.

6. Genetic Predisposition: Some individuals may have a genetic predisposition to developing osteochondral defects. A familial tendency has been observed in osteochondritis dissecans, suggesting that the structure or composition of cartilage and subchondral bone in certain individuals makes them more susceptible.

7. Joint Disorders: Conditions such as osteoarthritis, inflammatory arthritis (e.g., rheumatoid arthritis), or prior joint injury can lead to osteochondral defects as part of the disease process.

8. Idiopathic Causes: In some instances, osteochondral defects develop without a clear identifiable cause and are referred to as idiopathic defects.

Symptoms

- Pain: Pain is the most common symptom. It may be localized to the affected area and varies in intensity, often worsened by weight-bearing activities such as walking, running, or climbing stairs. In osteochondritis dissecans, pain is frequently felt over the medial femoral condyle and may be reproduced by the Wilson test — a maneuver in which internal tibial rotation during knee extension compresses the affected area.

- Swelling: Swelling around the knee joint may occur, especially after physical activity or prolonged standing. It is typically localized to the area of the defect.

- Stiffness: Stiffness in the knee, particularly after periods of inactivity or upon waking, can affect mobility and the ability to fully bend or straighten the knee.

- Catching or Locking Sensation: A catching or locking sensation during movement can occur if a loose fragment of cartilage or bone becomes displaced and interferes with normal joint motion. This is a hallmark sign that an osteochondritis dissecans lesion has progressed to fragment detachment.

- Decreased Range of Motion: The presence of an osteochondral defect can limit the knee's range of motion, making it difficult to fully extend or flex the knee.

- Instability: The knee may feel unstable or give way due to altered joint mechanics, impacting balance and increasing the risk of further injury.

- Weakness: Muscle weakness around the knee may develop as a result of pain and limited mobility.

- Grinding Sensation: In more advanced cases, a grinding sensation (crepitus) during knee movement can indicate roughened or irregular joint surfaces.

Diagnosis

Medical History and Physical Examination:
- Your healthcare provider will discuss symptoms including the location and nature of knee pain, swelling, stiffness, locking, or instability.
- They will also ask about your medical history, previous knee injuries, and activities that aggravate or relieve your symptoms. A history of sports participation during adolescence is particularly relevant for osteochondritis dissecans.
- During the physical examination, the provider will assess the knee for tenderness, swelling, range of motion, and signs of instability or joint locking. The Wilson test may be performed specifically to evaluate for osteochondritis dissecans.

Imaging Studies:
- X-rays: X-rays are the initial imaging study and can identify bony abnormalities, loose bodies, or changes in joint alignment. A tunnel view (notch view) X-ray is particularly useful for visualizing the posterior femoral condyle, the most common site of osteochondritis dissecans.
- MRI (Magnetic Resonance Imaging): MRI is the most sensitive and informative imaging study for both osteochondral defects and osteochondritis dissecans. It provides detailed images of the cartilage, subchondral bone, and surrounding soft tissues. MRI is essential for determining lesion size, location, and stability — specifically, whether fluid has tracked beneath the fragment (a sign of instability), and whether the overlying cartilage remains intact. This information directly guides treatment decisions.
- CT Scan: CT may be used for additional detail about bony architecture and surgical planning in complex cases.

A knee MRI is the definitive study for characterizing osteochondral lesions — it is the only imaging modality that can reliably assess lesion stability, cartilage integrity, and the presence of fluid beneath a fragment, all of which are critical for treatment planning.

Staging of Osteochondritis Dissecans on MRI:
MRI findings are used to classify osteochondritis dissecans lesion stability, which is the most important factor in determining treatment:
- Stage I: Subchondral bone signal change without cartilage disruption or instability.
- Stage II: Cartilage irregularity or fissuring, but the fragment has not separated.
- Stage III: Partially detached fragment — fluid is visible beneath the fragment on MRI, indicating instability.
- Stage IV: Completely detached loose body within the joint with an empty defect at the donor site.

Arthroscopy:
When the diagnosis remains uncertain or surgical intervention is being considered, arthroscopy may be performed. This minimally invasive procedure allows the surgeon to directly visualize the cartilage surface, probe lesion stability, and treat the defect at the same time.

Differential Diagnosis:
Your healthcare provider will also consider other conditions that may cause similar symptoms, such as meniscal tears, ligament injuries (e.g., ACL tear), or other types of cartilage damage.

Treatments

Conservative Management:
- Activity Modification: Avoiding high-impact activities that exacerbate symptoms, such as running and jumping. In skeletally immature patients with stable osteochondritis dissecans lesions, activity restriction alone — combined with close monitoring — can result in complete healing, making conservative care the preferred first-line approach in this population.
- Physical Therapy: A structured program to strengthen muscles around the knee, improve range of motion, and enhance joint stability. Modalities such as ultrasound or electrical stimulation may be used to reduce pain and inflammation.
- Orthotic Devices: Custom-made orthotics or braces may be used to unload the affected area of the knee and provide support.
- Crutches / Weight-Bearing Restriction: For osteochondritis dissecans in younger patients, a period of non-weight-bearing or protected weight-bearing is sometimes prescribed to reduce compressive forces on the lesion and encourage revascularization of the subchondral bone.

Medications:
- Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): These medications help reduce pain and inflammation.
- Pain Relievers: Analgesics may be prescribed to manage pain during flare-ups.

Injections:
- Corticosteroid Injections: Injections directly into the knee joint can provide temporary relief from pain and inflammation.
- Hyaluronic Acid Injections: Also known as viscosupplementation, these injections help lubricate the joint and reduce pain.

Biological Treatments:
- Platelet-Rich Plasma (PRP) or Stem Cell Therapy: These treatments involve injecting concentrated platelets or stem cells from the patient's own body into the knee joint to promote healing of the osteochondral defect. PRP has also been explored as an adjunct to surgical procedures for osteochondritis dissecans to enhance bone and cartilage healing.

Surgical Options:
- Drilling / Transarticular Drilling: For stable osteochondritis dissecans lesions with intact cartilage that have failed conservative management, drilling into the subchondral bone stimulates revascularization and promotes healing. This is one of the most common surgical interventions in the adolescent OCD population.
- Fragment Fixation: For partially detached (Stage III) osteochondritis dissecans fragments with viable bone, the fragment can be secured back in place using bioabsorbable pins, screws, or bone grafting techniques. Preserving the native cartilage is always the preferred goal when the fragment is salvageable.
- Arthroscopic Debridement and Microfracture: This minimally invasive procedure removes loose cartilage and stimulates new cartilage growth by making tiny fractures in the underlying bone. It is typically used for smaller defects with intact cartilage edges.
- Osteochondral Autograft Transplantation (OATS) / Mosaicplasty: Healthy cartilage and bone plugs are harvested from a lower-demand area of the knee and transplanted into the defect. This is suitable for larger defects, including those resulting from detached osteochondritis dissecans fragments.
- Osteochondral Allograft Transplantation: In cases where the defect is too large or complex for OATS, donor cartilage and bone tissue (allograft) can be used to resurface the damaged area.
- Autologous Chondrocyte Implantation (ACI): A small sample of healthy cartilage cells is harvested, grown in a laboratory, and then implanted into the defect during a second procedure. This technique is suited for larger defects and aims to regenerate new hyaline-like cartilage.
- Joint Replacement: In severe cases with extensive joint damage where other treatments have failed, total or partial knee replacement may be necessary to relieve pain and restore function.

Related Knee Conditions

• Avascular Necrosis (AVN) of the Knee
• Meniscus Tear
• ACL Tear
• Popliteal Cyst
• Jumper's Knee
• Back to all Knee Conditions