The talus, lined with articular cartilage, connects to the tibia and fibula to make up the ankle joint. An osteochondral injury occurs when the talus and/or surrounding cartilage is bruised, fractured, or chipped from an injury.
If the talus strikes the tibia or fibula during the twisting motion of an ankle sprain, its smooth surface may be injured. The injuries are ranked in four stages.
Stage 1 Injury
In a Stage 1 Injury, the articular surface is injured slightly.
Stage 2 Injury
In a Stage 2 Injury, the talus is partially fractured. Perhaps the fracture is not long enough to cause a bone chip.
Stage 3 Injury
In a Stage 3 Injury, the talus is completely fractured. The bone is chipped, but the fragment remains in place. This is likely to happen if the articular cartilage stays intact.
Stage 4 Injury
In a Stage 4 Injury, cartilage and the bone fragment break off and may move around within the ankle joint. Separated from its blood supply, the cartilage and bone fragment die, making the injury slow to heal.
Symptoms start like a sprained ankle - pain, swelling, and difficulty walking - which is why the injury may go undetected and get worse. If there is a bone fragment, there may be a catching sensation felt during movement.
Depending upon the extent of injury, treatment may include rest and ice, immobilization with a cast and crutches, or even surgery. During surgery, the bone fragment is removed and the talus is treated to promote healing.