The ankle joint is composed of the bottom of the tibia (shin) bone and the top of the talus (ankle) bone. The top of the talus is dome-shaped and is completely covered with cartilage—a tough, rubbery tissue that enables the ankle to move smoothly. An osteochondral lesion of the talus (OLT) is an area of abnormal, damaged cartilage and bone on the top of the talus bone (the lower bone of the ankle joint). It is also called an osteochondral defect (OCD) or talar osteochondral lesion (OCL). “Osteo” means bone and “chondral” refers to cartilage.
It is often caused by a traumatic injury, such as a severe ankle sprain. However, it can also occur from chronic overload due to malalignment or instability of the ankle joint. If the cartilage does not 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.
OCLs most commonly occur in two areas of the talus:
- The inside and top part of the lower bone of the ankle (the medial talar dome) or
- The outside and top part of the lower bone of the ankle (the antero-lateral talar dome).
Signs & Symptoms
Unless the injury is extensive, it may take months, a year or even longer for symptoms to develop. Patients can have three different kinds of complaints, whether or not in combination:
- Deep pain in the joint: typically worse when bearing weight on the foot (especially during sports) and less when resting.
- Locking sensation: sometimes, a piece of cartilage is only partially linked after some time. Because of that, it can pivot and move during a certain motion, which gives patients the feeling that something blocks the normal smooth movement of a joint. Something seems to jump.
- Instability: some patients complain after a sprain, e.g. of the ankle, of an unstable feeling, accompanied by pain. This may be due to a tear in the ligaments of the joint but also to the presence of a cartilage injury. When a certain movement causes pain, one can have the feeling of falling through the ankle, without it being unstable.
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 and will examine the foot and ankle, moving the ankle joint to help determine if there is pain, clicking or limited motion within that joint.
Plain x-rays can be used to help diagnose an osteochondral lesion although it is not uncommon for the plain x-rays to be read as normal. Often an MRI or other advanced imaging tests are ordered to further evaluate the lesion and extent of the injury.
Treatment depends on the severity of the talar dome lesion. If the lesion is stable (without loose pieces of cartilage or bone), one or more of the following non-surgical treatment options may be considered:
- Immobilization – 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 immobilization, nonweightbearing range-of-motion exercises may be recommended.
- Oral medications – Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, 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.
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:
- Exploratory arthroscopic operation with debridement and microfracture – in this case, there is an arthroscopic debridement of the cartilage injury, which is done through 2 small skin incisions and by means of a camera and other instruments. As a result, the pressure is reduced.
- Open surgery (arthrotomy or osteotomy) – same procedure as above, just not through an arthroscopic surgery.
- Osteochondral grafting (ACI, OATs, Mosaicplasty) – the osteochondral graft can either be taken from the knee, or consist of synthetic material.
- Osteochondral Allograft Transfer – A bone and cartilage plug may also be obtained from a cadaver and transplanted into the OCL. This prevents the need from harvesting bone and cartilage from another part of the body (eg. knee).