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.
The ankle joint is responsible for dorsiflexion (moving the toes up as when standing only on the heels) and plantar flexion of the foot (moving the toes down, as when standing on the toes), and allows for the greatest movement of all the joints in the foot. The ankle does not allow rotation.
In plantar flexion, the anterior ligaments of the joint become longer while the posterior ligaments become shorter. The reverse is true for dorsiflexion.
The lateral malleolus of the fibula and the medial malleolus of the tibia along with the inferior surface of the distal tibia articulate with three facets of the talus. These surfaces are covered by cartilage.
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 to those of 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 (Maisonneuve fracture), and to palpate the sole of the foot to look for a Jones fracture at the base of fifth metatarsal (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 the posterior portion of the talus is also fractured, this is called a trimalleolar fracture. 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). Open reduction and internal fixation (commonly known as ORIF) is usually performed with permanently implanted metal hardware that holds the bones in place while the natural healing process occurs. A cast may be required to immobilize the ankle following surgery. Trimalleolar fractures or those with dislocation have a high risk of developing arthrosis. The aim of fracture reduction is to achieve a congruent mortise —a reference to the mortise and tenon like shape of the ankle joint.
Mechanical instability of the lateral ankle ligaments can be treated by either the Evans Technique or the Broström procedure.