Given the mobility of the ankle joint and our bipedal existence, ankle injuries are a common complaint. They represent 14.6% of all visits to the ED.1 Fractures of the lateral malleolus are more prevalent in men younger than 50 years old and in women older than 50 years old.2,3 Previous ankle sprain and participation in sports like soccer, basketball, rugby, and football are risk factors for ankle injuries.4-7 A review of the National Electronic Injury Surveillance System in 2009 reported an incidence of ankle sprains of 206 per 100,000 people in the United States.8
The proximal part of the ankle mortise is comprised of the distal fibula and tibia that fits on top of the talus. These bones are wider anteriorly than posteriorly. Joint stability is provided by medial and lateral malleoli extending on either side of the talus. The medial deltoid ligament, lateral ligament complex, and syndesmosis are the three distinct groups of ligaments that stabilize the ankle9 (Figure 1). The deltoid ligament is the strongest of these ligaments and is a thick, triangular band of tissue originating from the medial malleolus. The lateral ligament complex consists of the lateral malleolus that attaches to the anterior and posterior aspects of the talus and calcaneus by the anterior talofibular, posterior talofibular, and calcaneofibular ligaments, respectively. This ligament complex, the anterior talofibular ligament in particular, is the weakest and most commonly injured in lateral sprains and represents 85% of all ankle sprains.10 The syndesmosis, which holds the tibia and fibula together, is a group of four distinct ligaments attaching the distal tibia to the fibula just above the talus (Figure 1). The syndesmosis allows the fibula to rotate and carries approximately 16% of the axial load.9
Ligaments of the ankle joint. A. The three lateral ligaments: the anterior and posterior talofibular ligaments and the calcaneofibular ligament. B. The four bands of the deltoid ligament: the anterior and posterior tibiotalar, the tibiocalcaneal, and the tibionavicular. C. Anterior and posterior view of the ankle syndesmosis. The ligaments of the syndesmosis are the anterior inferior tibiofibular ligament, the posterior inferior tibiofibular ligament, the transverse ligament, and the interosseous ligament, which connects the entire length of the tibia and fibula.
The ankle is considered a hinged joint, but ligamentous attachments allow for some rotation and translation within the mortise of the talar dome.9 Branches of the sciatic nerve, the superficial peroneal, deep peroneal, peroneal, and tibial, innervate the four muscle groups of the ankle joint with branches of the popliteal artery serving as the blood supply (Figure 2). The tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles run over the anterior aspect of the joint and are responsible for dorsiflexion. Inversion is accomplished by the tibialis ...