In human anatomy, the ankle joint is formed where the foot and the leg meet. The ankle, or talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus bone in the foot. The articulation between the tibia and the talus bears more weight than between the smaller fibula and the talus.
The term "ankle" is used to describe structures in the region of the ankle joint proper.
In plantar flexion, the anterior ligaments of the joint become longer while the posterior ligaments become shorter. The reverse is true for dorsiflexion.'''
The anterior talus is wider than the posterior talus. When the foot is dorsiflexed , the wider part of the superior talus moves into the articulating surfaces of the tibia and fibula, creating a more stable joint than when the foot is plantar flexed.
The joint is most stable in dorsiflexion and a sprained ankle is more likely to occur when the foot is plantar flexed. This type of injury more frequently occurs at the anterior talofibular ligament.
Most traumatic incidents involving the ankle result in ankle sprains. Symptoms of an ankle fracture can be similar than for sprains (pain, hematoma) or there may be an abnormal position, abnormal movement or lack of movement (if there is an accompanying dislocation), or the patient may have heard a crack.
On clinical examination, it is important to evaluate the exact location of the pain, the range of motion and the condition of the nerves and vessels. It is important to palpate the calf bone (fibula) because there may be an associated fracture proximally, and to palpate the sole of the foot to look for a Jones fracture or the base of fifth metacarpal fracture (avulsion fracture)
Evaluation of ankle injuries for fracture is done with the Ottawa ankle rules, a set of rules that were developed to minimize unnecessary X-rays. On X-rays, there can be a fracture of the medial malleolus, the lateral malleolus, or the anterior or posterior margin. If both malleoli are broken, this is called a bimalleolar fracture (some of them are called Pott's fractures). If three of these are broken at the same time, this is called a trimalleolar fracture (although there are only two malleoli). Ankle fractures are classified according to Weber, depending on their position relative to the anterior ligament of the lateral malleolus (type A = below the ligament, type B = at its level, type C = above the ligament). A special form of type C fracture is the Maisonneuve fracture, which involves a spiral fracture of the fibula with a tear of the distal tibiofibular syndesmosis and the interosseous membrane.
Only type A fractures of the lateral malleolus can be treated like sprains; all other types require surgery (most often an open reduction and internal fixation). A cast may be required to immobilize the ankle following surgery. Trimalleolar fractures or those with dislocation have a high risk of developing arthrosis.