What is it?
The ankle joint is composed of the bottom of the tibia (shin) bone, and the top of the talus (ankle) bone. The ankle bone transfers weight-bearing from the shin to the foot. The second largest of the tarsal bones, the talus has the highest percentage of surface area covered by cartilage in the entire human body. Unlike most bones, no muscles attach to the talus, so its position depends on that of the neighbouring bones.

The top of the talus is dome-shaped and is completely covered with cartilage which enables the ankle to move smoothly. A talar dome lesion is an injury to the cartilage and underlying bone of the talus within the ankle joint. It is also called an osteochondral defect (OCD) or osteochondral lesion of the talus (OLT). “Osteo” means bone and “chondral” refers to cartilage.

Talar dome lesions are usually caused by a traumatic fracture or an injury, such as an ankle sprain. When the bones in the ankle joint hit each other damaging the cartilage surface, if the cartilage doesn’t heal properly following the injury, it softens and begins to break off. Sometimes a broken piece of the damaged cartilage and bone will “float” in the ankle.The initial pain may resolve, but the pain often comes back during exercise, with possible locking of the joint.

Signs and Symptoms
Unless the injury is extensive, it may take months, a year, or even longer for symptoms to develop. The signs and symptoms may include:
• Chronic pain deep in the ankle, typically worse when bearing weight on the foot (especially during sports), and less when resting.
• An occasional “clicking” or “catching” feeling in the ankle when walking.
• A sensation of the ankle “locking” or “giving out”.
• Episodes of swelling of the ankle occurring when bearing weight, and subsiding when at rest.

Diagnosis
A talar dome lesion can be difficult to diagnose, because the precise site of the pain can be hard to pinpoint. To diagnose this injury, the surgeon will question the patient about recent or previous injury. An examination of the foot and ankle would also be done, moving the ankle joint to help determine if there is pain, clicking, or limitation of motion within that joint.
An x-ray and/or an MRI are usually done. Initial x-rays are taken to check the alignment of the foot and ankle, as well as look for any bone damage. With an MRI, the ligament structures, tendons, and cartilage of the ankle can be examined and analysed.

Treatment
Non-Surgical Approaches
Treatment depends on the severity of the lesion. If it is stable (without loose pieces of cartilage or bone), one or more of the following non-surgical treatment options may be considered:
• Immobilisation – Depending on the type of injury, the leg may be placed in a cast or cast boot to protect the talus. During this period of immobilisation, non-weight bearing range-of-motion exercises may be recommended.
• Oral medications – Nonsteroidal anti-inflammatory drugs may be helpful in reducing the pain and inflammation.
• Physical therapy – Range-of-motion and strengthening exercises are beneficial once the lesion is adequately healed. Physical therapy may also include techniques to reduce pain and swelling.
• Ankle brace – Wearing an ankle brace may help protect the patient from re-injury if the ankle is unstable.

When is Surgery Required?
If non-surgical treatment fails to relieve the symptoms of talar dome lesions, surgery may be necessary. Surgery may involve removal of the loose bone and cartilage fragments within the joint and establishing an environment for healing. A variety of surgical techniques is available to accomplish this. The surgeon will select the best procedure based on the specific case.

Complications
Depending on the amount of damage to the cartilage in the ankle joint, arthritis may develop in the joint, resulting in chronic pain, swelling and limited joint motion. Treatment for these complications is best directed by a surgeon, and may include one or more of the following:
• Non-steroidal or steroidal anti-inflammatory medications
• Physical therapy
• Bracing
• Surgical intervention.