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 softening of the cartilage layers, cyst-like lesions within the bone below the cartilage, or fracture of the cartilage and bone layers. Throughout this article, these injuries will be referred to as osteochondral lesions of the talus (OLT).