Osteochondral lesions, sometimes called osteochondritis dessicans or osteochondral fractures, are injuries to the talus (the bottom bone of the ankle joint) that involve both the bone and the overlying cartilage. These injuries may include blistering of the cartilage layers, cyst-like lesions within the bone underlying the cartilage, or fracture of the cartilage and bone layers. Throughout this discussion, these injuries will be referred to as osteochondral lesions of the talus (OLT).
Symptoms and Clinical Presentation
OLTs can occur after a single traumatic injury or as a result of repeated trauma. Common symptoms include prolonged pain, swelling, catching, and/or instability of the ankle joint. After an injury, such as an ankle sprain, the initial pain and swelling should decrease with appropriate recovery (rest, elevation). Persistent pain, despite appropriate treatment after several months, may raise concern for an OLT.
Pain may be felt primarily at the lateral (outside) or medial (inside) aspect of the ankle joint. Severe locking or catching symptoms, where the ankle freezes up and will not bend, may indicate that there is a large osteochondral lesion or even a loose body (loose piece of cartilage or bone free within the joint).
Cause (including risk factors)
The majority of OLTs (85%) occur after a traumatic injury to the ankle joint. Ankle sprains (rolling-inward injury to the ankle) are a common cause of OLTs. With this type of injury, a section of the talus surface may impact another part of the ankle joint (tibia or fibula). As this happens, an impaction, crush, or shearing injury to the talus may occur. Other types of injury mechanisms may also cause an injury to the surface of the talus.
The talus is the bottom bone of the ankle joint. Much of this bone is covered with cartilage. The tibia and fibula bones sit above and to the sides of the talus, forming the ankle joint. This joint permits much of the up (dorsiflexion) and down (plantarflexion) motion of the foot/ankle. The blood supply to the talus is not as rich as many other bones in the body, and as a result, injuries to the talus sometimes are more difficult to heal than similar injuries in other bones.
OLTs are diagnosed with a combination of clinical and special studies. Your orthopedic foot and ankle surgeon may have a suspicion that you have this type of injury from the history you provide. Physical examination can further increase the suspicion for this type of injury. Imaging is necessary to confirm the diagnosis. Occasionally, regular X-rays can show an OLT, but frequently additional imaging is needed. This additional imaging may be a CT scan or an MRI.
*Source: American Orthopaedic Foot & Ankle Society® http://www.aofas.org