The talus bone forms the lower part of the ankle joint, and its surface is covered by a thin layer of cartilage. This cartilage ensures that body weight is distributed evenly across the joint surface while walking and running. An osteochondral lesion is damage to this cartilage layer and the bone immediately beneath it. Even if the damaged area is small, the functional consequences can be serious — because cartilage cannot regenerate itself, untreated lesions cause early arthritis in the ankle over time.
About seventy percent of lesions develop after an ankle sprain or fracture. During a sprain, the talus collides with the tibia or fibula, and the cartilage and underlying bone are crushed or detached. In the remaining thirty percent there is no history of trauma; in these cases, a disturbance in the bone’s blood supply (an avascular cause) is held responsible. The most commonly affected areas are the medial (inner) and lateral (outer) corners of the talus.
Lesions are classified in four stages. Stage 1: bruising of the subchondral bone, with the cartilage surface intact. Stage 2: partial separation of the cartilage. Stage 3: the cartilage and the underlying bone fragment have completely separated but remain in place. Stage 4: the fragment has detached and circulates within the joint as a loose body. The stage plays a key role in determining the treatment method.
In stage 1 and 2 lesions, conservative treatment is tried first. Immobilization with a boot or cast without weight bearing is applied for six weeks, with the goal of allowing the subchondral bone to heal. While the success rate of conservative treatment is above fifty percent in stage 1 lesions, surgery is almost always necessary in stage 3 and 4 lesions.
The most commonly applied surgical technique is the arthroscopic microfracture method. After the damaged cartilage in the lesion area is cleaned, millimeter-sized holes are drilled into the underlying bone. Bone marrow cells and growth factors seep through these holes and fill the area with fibrocartilage (scar cartilage). In lesions smaller than one square centimeter, the success rate is above eighty percent.
In larger lesions (over one square centimeter), or in cases of failure after microfracture, advanced techniques come into play. In the OATS (osteochondral autograft transfer system) method, a healthy cartilage-bone cylinder taken from the knee is transplanted to the lesion area. Bone marrow concentrate applications supported by a collagen or synthetic scaffold are also among current options. Which technique to apply is determined by the size and location of the lesion and the patient’s activity level.
Postoperative rehabilitation varies by technique. After microfracture, the patient walks with partial weight for six to eight weeks, and full weight bearing begins at the twelfth week. After OATS this period is somewhat longer. Return to sports is usually possible between the fourth and sixth months. Adherence to the physical therapy protocol is critical — early loading disrupts cartilage healing, while delayed movement leads to joint stiffness.
The most important message about talus osteochondral lesions is this: if pain and swelling persist for weeks after an ankle sprain, do not settle for a diagnosis of "just a sprain." Have an MRI to assess whether there is cartilage damage. Early diagnosis increases the chance of a better outcome with simpler treatment.