”Broken feet” is a very common phenomenon in our daily life. Many people do not think it is a big deal. In fact, if you break your foot repeatedly, it can often lead to damage to the talar osteochondral bone. Talar osteochondral injury is a type of cartilage injury in the ankle joint (in addition to talar osteochondral injury, cartilage injury may also occur in the tibia) and is very common in clinical practice. The main manifestation is a partial detachment of the articular cartilage, which affects the deeper subchondral bone. (The subchondral bone is an important “shock absorber” and is also an important tissue affecting the metabolism of articular cartilage. It is important to note that osteochondral damage to the talus is not the same as osteoarthritis. Because osteoarthritis typically occurs over a large, diffuse, multiple area of damage. In contrast, osteochondral cartilage damage to the talus is generally a single lesion with a relatively limited extent of injury. In addition, there is some bias in the statement that osteochondral damage to the talus can lead to osteonecrosis of the talus for two reasons: 1. Strictly speaking, osteonecrosis of the talus is similar to osteonecrosis of the femoral head, which is caused by insufficient blood supply and other reasons. In contrast, osteochondral injury of the talus, also known as transchondral talus fracture, occult osteochondral fracture, etc. Most patients have the disease due to trauma, such as severe ankle trauma, fractures, and a long history of ankle sprains. The etiology of the two is different, and osteochondral damage of the talus is not the cause of osteonecrosis of the talus. 2. Osteonecrosis of the talus usually causes extensive necrosis. In contrast, osteochondral injury of the talus is a localized necrosis with a lesion diameter of about 1 cm. Even if the lesion continues to expand, the vast majority will not develop into extensive, widespread osteonecrosis of the talus. When osteochondral injury of the talus occurs, patients often feel pain and swelling in the ankle, especially if they have been walking for a longer period of time. In the early stages of the disease, the pain can be relieved with rest, and when the disease progresses to a later stage, the patient will feel pain even when resting. This pain is not unbearable and severe, but mainly soreness. In addition, some patients may occasionally feel a rubbing sensation when the ankle is turned. This is because after the cartilage is damaged, the surface becomes rough and uneven, and the friction becomes greater. As the talar osteochondral injury progresses, cystic degeneration may also occur over time. “Cystic degeneration is a chronic lesion in which part of the subchondral bone is slowly resorbed and the bone tissue is reduced, gradually turning into a cavity. Cystic degeneration occurs after an injury to the talar osteochondral bone because, on the one hand, the cartilage on the surface of the talus is damaged and the joint fluid seeps into the subchondral bone. The “fluid” in the subchondral bone grows and eventually a cavity is formed inside. On the other hand, when the cartilage is damaged, the joint loses its “shock absorber” and the pressure on the subchondral bone becomes greater, and over time, the internal bone may develop small fractures and necrosis, slowly atrophying and eventually forming a cavity. It is not difficult to diagnose osteochondral injury of the talus, and X-ray is the easiest test. However, because of the high rate of missed X-rays, it is necessary to do MRI in addition to X-rays for diagnosis. So, why not do a CT exam? Because on a CT film you can only see the bones, not the cartilage. MRI can show the articular cartilage, subchondral bone, fibrocartilage, joint fluid and granulation tissue more accurately, and the scope and extent of the injury can be accurately determined by MRI, which provides an important basis for treatment. In addition, some patients with swollen ankles worry that the swelling will affect the diagnostic results when they have an MRI examination and want to wait until the swelling subsides, but this concern is completely unnecessary. This concern is totally unnecessary because MRI examination can see the “essence” of cartilage damage through the “appearance” of swelling, and then make accurate judgment.