Anatomy

The ankle is composed of two joints: the talar mortise and the subtalar joint. The talar joint is a modified hinge joint similar to a “mortise and tenon,” as referred to in carpentry. It is composed of three bones: the tibia, the mortise, and the talus of the fibula, which form the tenon (Fig. 85.1). The plafond or “ceiling” of this joint is formed by the tibia with its medial malleolus and articulation with the fibula.

Fig. 85.1 Bony anatomy of the ankle.

The dome of the talus has a trapezoidal shape—wider anteriorly and narrower posteriorly. This anatomic shape confers greater stability in dorsiflexion. However, when the ankle moves into plantar flexion, the narrow part of the talus sits in the mortise, which results in ankle instability and predisposes it to injury.^2,3

Ligaments of the Ankle

The medial side of the ankle is supported by the deltoid ligament (Fig. 85.2). The deltoid ligament has five components: one deep and four superficial. The deep ligament attaches to the tibia and the undersurface of the talus. The superficial ligaments are the tibionavicular, anterior talotibial, calcaneotibial, and posterior talotibial.

Fig. 85.2 Medial ligaments of the ankle.

The lateral aspect of the ankle has three supporting ligaments: the anterior talofibular, calcaneofibular, and posterior talofibular (Fig. 85.3). The tibiofibular ligaments include the anterior and posterior inferior ligaments, which bind the distal ends of the tibia and fibula, and the superior ligaments of the same name, which bind the tibia and fibula at the proximal articulation. Other supporting structures are the inferior transverse ligament and the interosseous ligament. The latter is not part of the ankle but nevertheless provides a strong bond between the tibia and fibula.^2,3

Fig. 85.3 Lateral ligaments of the ankle.

History and Physical Examination

A methodic approach to elicitation of the history of the injury and examination of the ankle joint is of paramount importance. Frequently, the mechanism is unknown because of the sudden and rapid occurrence of the injury. Specific questions about the mechanism, time of the injury, ability to bear weight, and previous history of injury involving the affected joint are helpful in arriving at an accurate diagnosis (Box 85.1).

The physical examination (Box 85.2) should be thorough and orderly with the intent of assessing joint stability and possible neurovascular compromise. The emergency physician (EP) should make sure that the patient is in a comfortable position for the examination. Many times patients are examined in hallways while sitting in chairs with their feet resting on the floor or a wheelchair footrest. Uncomfortable approaches to examination of the ankle—or any joint for that matter—are detrimental to the welfare of both the patient and physician. All that is derived from this approach is an incomplete examination and an uncomfortable patient and physician.

The EP should make sure that the patient is seated at a level higher than the examiner (e.g., seated on a gurney with the affected limb dependent, seated on the examining table with both extremities on the table). Never begin the examination at the point of maximal swelling and tenderness. The examination should begin with visual inspection to assess the degree of swelling and the presence of any deformity and discoloration. The neurovascular status of the extremity is evaluated by testing sensation, capillary refilling, and presence of pulses. Once a preliminary assessment is done, the EP should proceed in detail from distal to proximal in an orderly fashion as noted in Box 85.2.⁵

Other Maneuvers

Other maneuvers sometimes used in the evaluation of an injured ankle are worth mentioning. The anterior drawer test (Fig. 85.4) is used to determine the integrity of the anterior talofibular ligament. It is, unfortunately, not very reliable, especially in acute injuries with significant swelling and pain. It is performed by holding the foot at the calcaneus with one hand while the other hand stabilizes the extremity at its middle third. The foot is moved forward while one observes or feels (or both) for displacement of the foot and ankle anteriorly.

Fig. 85.4 Anterior drawer test.

The side-to-side test (clunk test) evaluates the integrity of the tibiofibular ligament. The foot is held in a neutral position and then moved from side to side. A “clunk” is heard or felt if the ligament is ruptured.

The talar tilt test can be used to assess the deltoid ligament and the calcaneofibular ligament by applying eversion and inversion stress, respectively. The calcaneus is held in one hand while the examiner moves the ankle into inversion or eversion (Fig. 85.5). Frequently, it is accompanied by simultaneous radiographic evaluation to determine the amount of tilt at the level of the talus.²

Fig. 85.5 Talar tilt test.

Stress testing is not generally performed in the acute phase of an injury because of its inaccuracy and the pain that it inflicts on the patient. Since the advent of magnetic resonance imaging (MRI), which can reveal soft tissue injuries of varying degrees, stress testing is rarely used at all.²

Classification of Ankle Sprains