of the medial malleolus into the subcutaneous tissue. Pathophysiology The Maisonneuve fracture generally follows a specific pattern of injury. The following are described as subsequent events that result in a Maisonneuve fracture: Forceful, external rotation of the ankle joint results in the tearing of the deep deltoid ligament and/or an avulsion fracture of the medial malleolus. The ankle mortise is subjected to excessive torque, rupturing the syndesmotic ligaments and anteromedial ankle joint capsule. Rotative energy is transferred upwards along the interosseous membrane, damaging it in the process. The force results in a spiral, sometimes an oblique, fracture at the neck of the proximal fibula. In cases where the anterior aspect of the tibiofibular syndesmosis can resist mechanical stress, only an oblique fracture of the lateral malleolus is produced. Diastasis of the lateral malleolus may also occur, in which it is posterolaterally displaced from the tibia. Although most Maisonneuve cases report a pronation-external rotation mechanism of injury, clinical studies have recorded instances of supination-external rotation being the mechanism of injury. Slight or high degrees of plantarflexion prior to supination-external rotation of the foot have been identified in patients with proximal fibular fractures. Diagnosis Diagnosing a Maisonneuve fracture requires a combination of medical history, physical examination, and radiographic imaging. Patients generally do not report pain near the proximal fibula, so physical examination such as palpation along the fibula is effective for differentiating a Maisonneuve fracture from an isolated syndesmotic injury. Feeling pain near the proximal fibula during palpation is a positive indication of a Maisonneuve fracture. Ankle instability is often associated with a damaged proximal fibula in a Maisonneuve fracture, so patients are typically asked about the mechanism of injury. Mortise stability is examined to rule out the possibility of an isolated fibular fracture. Ankle radiographs are used to detect widening of the tibiofibular syndesmosis or medial clear space. The medial clear space is the area between the talus of the ankle and the medial malleolus. Damage to the deltoid ligament and syndesmotic ligaments result in mortise instability, causing the talus to laterally shift and widen the medial clear space. A clinical study, conducted in 2006 and published in the Journal of Bone and Joint Surgery, found that the medial clear space size of a normal ankle and an injured ankle measured at 4 millimetres and 5.4 millimetres in length respectively. To confirm diagnosis, full-leg radiographs are used to inspect for fractures