An ankle fracture is a break in the far end of one of the 2 bones of the lower leg: the tibia (the inside or medial bone of the lower leg) and the fibula (the outside or lateral bone of the lower leg). Both bones end in a bony prominence (malleolus) that forms an arch on top of the talus, one of the bones of the foot. The ankle is a major weight-bearing hinge joint composed of three bones: the distal tibia, distal fibula, and talus. These 3 bones are joined together by 3 groups of ligaments that hold the ankle joint in place. The deltoid ligament is on the inside of the ankle, the lateral ligament complex is on the outside of the ankle; another group of ligaments holds the tibia and fibula together. The talus itself is usually not included in a diagnosis of ankle fracture.
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Ankle fractures occur most commonly when there is a sudden twisting injury to the foot. The ankle may roll in (inversion injury) or out (eversion injury), and the force on the foot can be transmitted to the tibia and fibula, resulting in fracture. The physician will often try to ascertain exactly how the injury occurred. Knowing the position of the ankle at the time of injury can help determine the mechanism of injury, which gives important information about which bones and ligaments were probably damaged. Fractures also can occur in individuals with unstable ankle joints and a history of recurrent ankle sprains.
As with other types of fractures, ankle fractures are described as either displaced or nondisplaced. In a displaced fracture, the fractured bone segments have moved out of alignment, while in a nondisplaced ankle fracture they have not. Any type of ankle fracture can affect the joint surface and joint motion (articulation) and almost always involves concomitant ligament injuries.
The prominent malleolar surfaces on the medial and lateral sides of the ankle are the most commonly injured areas. When one of the three bony prominences is fractured, the break is referred to as an isolated malleolus fracture. A fracture involving two malleolar prominences is called a bimalleolar fracture, and fracture of both malleoli and the posterior portion of the tibia is a trimalleolar fracture.
Risk: Individuals who participate in activities that potentially place excessive force on the ankle joint (e.g., skiing, snowboarding, ice skating, basketball, football, soccer, rugby) are at risk for ankle fractures. Ankle fractures commonly occur in motor vehicle accidents where the foot is braced against the floorboard. Most males experiencing ankle fractures are under age 50, while most women experiencing ankle fractures are over age 50 (Iskyan).
Incidence and Prevalence: In the US, the ankle is the joint most commonly injured. About 90% of sports-related injuries are ankle sprains, and 10 to 15% are ankle fractures (Steele). The incidence in the general US population is 187 per 100,000 person-years (Iskyan). As the population ages, the incidence of ankle fractures is increasing.
Source: Medical Disability Advisor