The cartilage surfaces of the ankle joint can be damaged when an ankle sprain or fracture occurs. As the ankle twists, the edge of the talus bone impacts the adjacent bone which bruises or shreds the cartilage. This may lead to small cracks in the cartilage or even formation of a hole or cyst underneath the surface. These various types of damage are called osteochondral defects (OCD) of the talus (an older term was osteochondritis dissecans).
There are different grades of severity of an osteochondral injury to the talus. Minor events lead to bruising of the talus. If the injury is more severe, large pieces of bone and cartilage can break off and lie loose in the ankle joint.
Symptoms of an osteochondral injury of the talus include:
• Continuous or intermittent pain
• Ankle instability or giving way
• Stiffness of the ankle
• Difficulty with walking, running, or sports
A foot and ankle specialist can diagnose an osteochondral injury of the talus by taking a medical history and conducting a physical exam. X-rays of the ankle are routinely obtained but may not identify an OCD in almost 50% of cases. Often, a CT scan or MRI may be needed to confirm the diagnosis and determine the location and size of the damage.
Treatment depends on the severity of the osteochondral injury. If only bruising of the bone is present, resting the ankle may be all that is required. Many times, the initial injury to the talus is more severe with structural damage and worse symptoms. Immobilization of the ankle, medications, steroid injections and physical therapy are commonly tried but this often fails to relieve symptoms and surgery may be required.
The treatment for an osteochondral defect of the talus is extremely varied and depends on the size of the defect and the extent of bone and cartilage loss. The most common surgical treatment is arthroscopy of the ankle. Multiple tiny incisions are made around the ankle and a small camera is inserted to inspect the joint. Small instruments are then inserted into the joint to clean out inflammation and debris. A microfracture can then be performed by drilling holes into the underlying bone to fill the crater with a blood clot containing proteins and cells to restore a smooth surface. This technique is effective in approximately 85% of cases.
Occasionally, more extensive surgeries may need to be performed for cartilage repair. These can range from bone grafting to more sophisticated treatments in which portions of the talus have to be replaced using large grafts obtained from the patient’s knee or from a cadaver.
Recovery from these procedures depends upon the extent of the defect and whether it can be treated arthroscopically or through open incisions.