Osteochondrosis dissecans (OD) – a condition affecting the bone and cartilage in the knee and ankle joints

The exact cause of osteochondrosis dissecans (OD) remains unclear to this day. Possible causes under discussion include repeated microtrauma, mechanical overload from sports, misalignment of the leg axis (bowlegs/knock-knees), or obesity, as well as local circulatory disorders, hormonal influences, and a genetic predisposition. The development of osteochondrosis dissecans appears to be a complex process and primarily affects joints subject to heavy stress, such as the knee and ankle. Constant compressive stress within the joint can disrupt blood flow in the bone to such an extent that cartilage and bone tissue may become detached. This process can lead to the death of bone tissue, a condition known as avascular necrosis. 

Illustration of a knee joint with an OD lesion on the femur—osteochondrosis dissecans most commonly affects the inner part of the femur.

Initially, the condition is often asymptomatic. However, as the damage progresses, pain may occur in the affected joint, usually related to weight-bearing and localized to the knee or ankle joint. A typical symptom is a dull pain after prolonged walking, running, or physical activity.
As the condition progresses, swelling may develop, mobility becomes restricted, and the joint may feel unstable. If a fragment detaches completely, it can lead to sudden locking, impingement, or a snapping sensation. At this stage, doctors refer to it as a “joint mouse.” If left untreated, the condition can lead to permanent limitations in movement and premature osteoarthritis.

Diagnosis begins with a review of the patient’s medical history and a clinical examination, during which local tenderness, joint locking, joint effusion, and restricted movement are assessed.
X-rays may show a localized area of increased density in the affected bone. However, this is usually not visible in the early stages. Magnetic resonance imaging (MRI) is the method of choice for an accurate assessment of the lesion and its stability. It allows for evaluation of the cartilage coverage, the stage of the disease, and the stability of the dissected fragment. Computed tomography (CT) can be used to accurately assess the extent of the bony defect, particularly in advanced stages. In some cases, diagnostic arthroscopy is performed as a supplementary procedure to directly inspect the joint surface and perform a manual stability assessment.
MRI correlation provides the best assessment of the stability of the lesion and the surrounding cartilage. A follow-up examination after three to six months is crucial in conservative therapy to detect healing or progression of the lesion at an early stage and to respond accordingly.

OD is aseptic bone necrosis characterized by the loss of bone tissue without the presence of infection. The disease progresses in stages. Although various classification systems exist in the literature, they all distinguish between stable and unstable cartilage-bone lesions.

In the early stage, the cartilage is still intact and the bone is only slightly damaged. In this phase, the condition can heal with rest and conservative treatment. In the intermediate stages, cracks and instability in the cartilage-bone junction are already evident. The dissected fragment may be partially detached but often remains anchored in the defect bed. In the advanced stage, the fragment eventually detaches completely, leading to the formation of a loose body. 

The course of the disease depends heavily on the patient’s age and the stage of the condition. In the juvenile form, the ability to heal spontaneously is significantly better, whereas surgical intervention is more frequently required in adults. The size of the defect and its location within the articular surface significantly influence the prognosis and treatment strategy. 

In early stages, conservative treatment is possible, particularly for the juvenile form of OD. The primary focus is on relieving stress on the affected joint. Sports activities are reduced, and depending on the findings, the joint is immobilized or subjected to partial weight-bearing for several weeks. Oral supplementation with vitamin D and calcium—essential substrates for bone metabolism—also plays an important role, particularly if bone edema is detected on MRI scans.

Physical therapy aims to maintain mobility and strengthen the surrounding muscles. Regular follow-up MRI scans are important for assessing the healing process. If findings remain stable, healing can be achieved without surgery. The observation phase typically lasts three to six months and is accompanied by regular radiological follow-ups. This is followed by a gradual load-bearing exercise program to restore joint stability and support the healing of the bone-cartilage complex.

If conservative treatment does not lead to a reduction in symptoms or an improvement in findings on radiological follow-up exams, or if the dissecans has already become detached, surgical treatment is necessary. The goal is to restore the stability of the joint surface and prevent the detachment of a cartilage-bone fragment. 

Depending on the stage and location, different surgical procedures are used. If the cartilage is intact or the cartilage-bone lesion is stable, the affected area can be drilled to stimulate blood flow and bone healing. This method is called retrograde drilling.
For smaller cartilage defects, bone marrow-stimulating procedures may also be performed to promote the formation of new cartilage. In cases of unstable, larger fragments, an attempt is often made to reattach them using absorbable pins, which are completely absorbed over time. If the dissected fragment is partially detached, it is reduced and fixed in place with small screws or pins made of absorbable material. In cases of non-repositionable, completely detached larger fragments, the fragment is removed and the defect is filled with the patient’s own bone and cartilage tissue (cartilage cell transplantation).

Whenever possible, treatment of OD is performed entirely arthroscopically, i.e., using a minimally invasive approach. In many cases, however, open surgery is necessary. Axial deviation (bowlegs/knock-knees) must be considered as a possible cause of OD and addressed as part of the surgical treatment. An axial-centering corrective osteotomy can reduce excessive stress on the affected joint compartment, which has a direct impact on the further course of the disease.

Osteochondrosis dissecans most commonly occurs in the knee, specifically on the inner thigh bone. Here, the risk factors mentioned above lead to a local disturbance in blood flow, resulting in gradual damage to the bone and the overlying cartilage.

Patients usually complain of pain on the inner side of the knee joint, which worsens with weight-bearing. Early diagnosis is crucial to avoid surgical intervention whenever possible. In advanced stages, however, where the dissecatus has become detached, only surgical stabilization of the fragment or removal of the fragment—with cartilage/bone reconstruction if necessary—can preserve joint function.

The upper ankle joint can also be affected by osteochondrosis dissecans, most commonly in the area of the talus (ankle bone). Typical symptoms include pain during weight-bearing and, occasionally, joint locking. The condition often has a chronic course and is frequently diagnosed at a late stage.

As with the knee, the choice of treatment depends on the stage of the disease. In early stages, conservative treatment involving weight-bearing restriction and targeted physical therapy can be successful, whereas advanced defects require surgical intervention.

The prognosis depends heavily on the stage of the disease at the time of diagnosis and the patient’s age. Overall, it is favorable if the condition is detected early and treated appropriately. The juvenile form of OD has a greater capacity for self-healing. In contrast, adult forms more frequently result in permanent damage to the articular surface and surrounding tissues. The progression of OD through its various stages is influenced by several factors, including the cause of the condition, the extent and location of the defect, and the stability of the affected articular surface. 

If OD is detected and treated in a timely manner, joint function can be fully restored in most cases. However, if left untreated, the condition can lead to persistent symptoms, reduced load-bearing capacity, and early-onset osteoarthritis. Studies show that long-term outcomes following early treatment are good in up to 80 percent of cases. In adults, the risk of osteoarthritis or recurrence is higher than in adolescents.

What is osteochondrosis dissecans?
Osteochondrosis dissecans is a condition affecting bone and cartilage in which a well-defined area of bone within the joint becomes detached due to impaired blood flow. This detached fragment is called a dissecate and can develop into a loose body within the joint. The condition most commonly affects the knee joint; less commonly, it affects the ankle or elbow joints. 

What are the causes of osteochondrosis dissecans?
The exact cause of osteochondrosis dissecans is not fully understood. Repeated microtrauma and overuse play an important role, particularly in athletically active adolescents. Other relevant risk factors include leg alignment abnormalities (bowlegs/knock-knees), obesity, localized circulatory disorders, hormonal influences, and genetic predisposition. Constant stress can disrupt blood flow within the bone, leading to bone necrosis. 

What are the symptoms of osteochondrosis dissecans?
The symptoms of osteochondrosis dissecans usually develop gradually. Typical symptoms include pain in the affected joint—especially the knee—that worsens with activity. Initially, the pain occurs only during prolonged activity; later, it may also occur at rest. In advanced stages, swelling, restricted movement, and joint locking may occur once the osteochondral fragment has completely detached and become a “joint mouse.” 

What does the term “juvenile osteochondrosis dissecans” mean?
Juvenile osteochondrosis dissecans occurs in children and adolescents with open growth plates. It differs from the adult form in its greater capacity for self-healing due to improved blood supply to the bone. With timely rest, the affected bone tissue usually heals completely. 

How is the condition diagnosed?
The diagnosis is initially made using X-rays, supplemented by magnetic resonance imaging (MRI), which shows the stage of the disease and the stability of the dissected fragment. If the findings are unclear, diagnostic arthroscopy may also be performed to accurately assess the joint surface. MRI is also important for discussing the course of the disease, the potential for self-healing, and the most appropriate treatment with the patient.

How is osteochondrosis dissecans treated?
Treatment for osteochondrosis dissecans depends primarily on the stage of the disease. In early stages, conservative treatment involves resting the affected joint for several weeks, accompanied by physical therapy. If conservative therapy fails or in advanced stages with a detached dissecatus fragment, surgical interventions are employed. These include retrograde drilling, refixation or removal of the fragment, and repair of the defect using a cartilage-bone graft. Concomitant surgical procedures, such as an axial-centering corrective osteotomy for bowlegs or knock-knees, must also be considered. The literature shows good long-term outcomes when the joint surface is stabilized early on.

What is the course of osteochondrosis dissecans?
The course of osteochondrosis dissecans depends heavily on the patient’s age and the stage of the disease at the time of diagnosis. In early stages, the affected bone area can regenerate through new blood vessel formation. In advanced stages, the fragment has completely detached, and surgery is unavoidable. The disease often progresses over months to years and requires consistent follow-up care.

What is the prognosis for osteochondrosis dissecans?
The prognosis for osteochondrosis dissecans is favorable with early diagnosis, particularly in adolescent patients with an open growth plate. Conservative treatment can lead to complete healing in these cases. In adults or with advanced lesions, the prognosis is poorer. If left untreated, there is a risk of damage to the joint surface and the development of premature osteoarthritis. Regular follow-up visits and attention to the mechanical axis of the leg are important to prevent further stress-related damage and to increase the likelihood of success for surgical cartilage-bone repair. 

Patients with osteochondrosis dissecans benefit in the long term from consistent follow-up care and regular checkups. For patients with OD in the knee joint, the prognosis is particularly good if the diagnosis is made at an early stage and weight-bearing is restricted promptly.

Which joints are most commonly affected? The knee
joint is most commonly affected, specifically the area of the inner thigh bone. The condition occurs less frequently in the ankle or elbow. 

When should you see a specialist?
Patients with osteochondrosis dissecans should consult a specialist in orthopedics and trauma surgery at an early stage. A specialist can assess, based on medical history, clinical examination, and imaging, whether conservative or surgical treatment is necessary. Accurate diagnosis is particularly important in cases of persistent symptoms or recurrent joint locking to prevent long-term complications such as osteoarthritis.