CHAPTER 11 The ankle

Approximately 14% of all sports injuries are sprains to the ankle, representing one ankle injury each season for every 17 participants. In high risk sports, such as jumping and running, this percentage is even higher, at 25% of all lost-time injuries (Reid, 1992). Ankle sprain has been shown to be 2.4 times more common in the dominant leg, and to have a high (73.5%) prevalence of recurrence (Yeung et al., 1994).

The joint mechanics of the ankle and foot have been described in Chapter 7. The ankle joint is the articulation between the trochlear surface of the talus and the distal ends of the tibia and fibula. The fibula may support 15–20% of the body weight (Lambert, 1971), with the fibula moving downwards and laterally during the stance phase of running to deepen the ankle mortice and enhance stability. This fibular motion creates tension in the interosseous membrane and tibiofibular ligament to provide some shock attenuation. Loss of this mechanism through tibiofibular disruption greatly affects the ankle joint, with a 1–2 mm lateral shift of the fibula increasing joint forces by as much as 40% (Reid, 1992).

Keypoint

The fibula can support up to 1/5 of the bodyweight and moves during the stance phase of running to deepen the ankle mortice and enhance ankle stability.

The ankle is subjected to considerable compression forces during sport (Fig. 11.1). Compression forces as high as five times body weight have been calculated during walking and up to 13 times body weight during running (Burdett, 1982).

Figure 11.1 Compression forces on the talus during running.

From Burdett, R.G. (1982) Forces predicted at the ankle during running. Medicine and Science in Sports and Exercise, 14, 308. With permission.

Collateral ligaments

The joint is strengthened by a variety of ligaments, the collaterals being the most important from the point of view of injury. Both medial and lateral collateral ligaments travel from the malleoli, and have bands attaching to the calcaneus and talus.

The medial (deltoid) ligament (Fig. 11.2A) is triangular in shape. Its deep portion may be divided into anterior and posterior tibiotalar bands. The more superficial part is split into tibionavicular and tibiocalcaneal portions, which attach in turn to the spring ligament. The lateral ligament (Fig. 11.2B) is composed of three separate components, and is somewhat weaker than its medial counterpart. The anterior talofibular (ATF) ligament is a flat band 2–5 mm thick and 10–12 mm long which travels from the anterior tip of the lateral malleolus to the neck of the talus, and may be considered the primary stabilizer of the ankle joint (Palastanga, Field and Soames, 1989). The posterior talofibular (PTF) ligament travels almost horizontally from the fossa on the bottom of the lateral malleolus to the posterior surface of the talus. Lying between the ATF and PTF ligaments is the calcaneofibular ligament, arising from the front of the lateral malleolus to pass down and back to attach onto the lateral surface of the calcaneum. The role of the collateral ligaments in maintaining talocrural stability is summarized in Table 11.1.

Figure 11.2 The ankle ligaments. (A) Deltoid (medial). (B) Lateral.

Table 11.1 Role of the collateral ligaments in ankle stability

Movement	Controlled by
Abduction of talus	Tibiocalcaneal and tibionavicular bands
Adduction of talus	Calcaneofibular ligament
Plantarflexion	ATF ligament and anterior tibiotalar band
Dorsiflexion	Posterior tibiotalar band and PTF ligament
External rotation of talus	Anterior tibiotalar and tibionavicular bands
Internal rotation of talus	As above with ATF ligament

Adapted from Palastanga, Field and Soames (1989).

Injury

The most common injury to the ankle is damage to the ATF ligament with or without involvement of the peroneus brevis. The subtaloid and mid-tarsal joints may be involved, but will be dealt with separately for clarity. The typical history of ankle injury is one of inversion, sometimes coupled with plantarflexion. The athlete ‘goes over’ on the ankle, usually on an uneven surface. One of three grades of ligament injury may occur.

Keypoint

The anterior talofibular (ATF) ligament is 2–5 mm thick and 10–12 mm long, approximately the width of the index finger. Its fibres run roughly parallel to the sole of the foot. Injury to the ATF is the most common sports injury affecting the ankle.

Swelling

There is usually an egg-shaped swelling in front of, and around, the lateral malleolus. When viewed from behind, the definition of the Achilles tendon is a good indicator of severity of injury (Reid, 1992). With more severe injuries (grade III) the definition of the Achilles tendon is lost due to excessive bleeding into the joint (Fig. 11.3).

Figure 11.3 Assessing severity of ankle injury from swelling. (A) Normal joint. Contour of Achilles tendon well defined. (B) Grade I/II injury. Clear swelling but Achilles tendon outline still visible. (C) Grade III injury. Profuse swelling obscures outline of Achilles tendon.

Objective measurement of swelling is made using the figure-of-eight measure, a valid and reliable measure (Mawdsley, Hoy and Eerwin, 2000; Rohner-Spengler, Mannion and Babst, 2007). For this test the end of a tape measure is placed on the anterolateral aspect of the ankle midway between the tibialis anterior tendon and the lateral malleolus. The tape is passed medially over the dorsum of the foot to the tuberosity of navicular and then beneath the plantar aspect proximal to the tubercle of the 5th metatarsal. The tape passes medially once more to rest distal to the medial malleous and is pulled across the Achilles back to the starting point.

Manual evaluation

The lateral malleolus should be gently palpated to assess if bone pain is present; if it is, an x-ray may be required (see below). If palpation reveals tenderness below, rather than over, the lateral malleolus and the athlete is able to bear weight, there is a 97% probability of soft tissue injury alone (Vargish and Clarke, 1983). Any fracture that is missed by this type of close palpation is likely to be an avulsion or non-displaced hairline type that will respond favourably to management as a sprain (Garrick and Webb, 1990).

Stress tests to the ankle are useful to assess the degree of instability in the subacute phase, and to give a differential diagnosis. Acute injuries may be exacerbated by full range motion with overpressure. The capsule of the ankle joint itself is assessed by passive dorsiflexion and plantarflexion only, the capsular pattern presenting as a greater limitation of plantarflexion. However, as the ankle ligaments span the subtaloid and mid-tarsal joints, inversion/eversion and adduction/abduction are also included in ankle joint examination.

The ATF ligament is placed on maximum stretch by passive inversion, plantarflexion, and adduction. The heel is held with the cupped hand and the subtaloid joint inverted. The opposite hand grasps the forefoot from above and swings it into plantarflexion and adduction. In addition, anterior glide of the talus on the tibia should be assessed with the foot in a neutral position. The heel is again held in the cupped hand, but this time the palm of the opposite hand is over the anterior aspect of the lower tibia. The calcaneus and talus are pulled forward as the tibia is pushed back. Movements are compared with that of the uninjured side for range and quality.

Keypoint

The ATF ligament is tested by passive inversion, plantarflexion and adduction. The athlete’s heel is held with the cupped hand and the heel is twisted inwards. The opposite hand grasps the forefoot from above and draws down and in.

The calcaneocuboid ligament is stressed by combined supination/adduction and the calcaneofibular ligament by inversion in a neutral position. The medial collateral ligament is stressed by combined plantarflexion/eversion/abduction (anterior fibres) or eversion alone (middle fibres). Resisted eversion will not be painful unless the peronei are affected (see below).

Ligamentous laxity may be assessed using the anterior draw test when acute inflammation has subsided. The patient’s foot is placed in slight (10−15°) plantarflexion and the heel is gripped with the therapist’s cupped hand, while the other hand stabilizes the lower tibia and fibula. The heel is drawn forwards against an opposite force pressing the tibia backwards and the amount of anterior movement is noted if the talus moves out of the ankle mortice. The test determines the integrity of both the anterior talofibular ligament and the calcaneofibular ligament and has been shown to be valid when compared to surgical observation (van Dijk et al., 1996).

Keypoint

The anterior draw test assesses ligamentous laxity, and is most useful when acute inflammation and muscle spasm have subsided.

Following severe ankle sprain or fracture, a bony link may form between the tibia and fibula (tibiofibular synostosis). Typically, pain occurs after an injury, and increases during vigorous activity, mimicking stress fracture. Pain is most severe during the push-off action of running and jumping, and dorsiflexion is often limited to 90°, mimicking impingement pain (see below). The synostosis is revealed by x-ray and removed surgically (Flandry and Sanders, 1987).

X-ray

Accurate physical examination will usually give sufficient information to preclude fracture, making x-ray unnecessary in most cases. Only 15% of patients suffering an acute ankle injury may have a fracture, and the Ottawa Ankle Rules provide a highly accurate clinical decision guide in this respect (Stiell et al., 1994). The rules state:

• An ankle x-ray is only needed if there is pain in the distal 6 cm of the malleolar region, together with an inability to bear weight and point tenderness of bone at the posterior edge or tip of the lateral malleolus or medial malleolus.

• A foot x-ray is only required if there is pain in the midfoot, an inability to bear weight or bone tenderness to the base of the 5th metatarsal or navicular.

A poster describing the rules is free to download at www.ohri.ca/emerg/cdr/docs/cdr_ankle_poster.pdf.

In a systematic review of 27 studies (15 581 patients) Bachmann et al. (2003) found the sensitivity of the Ottawa Ankle Rules to be almost 100% and claimed that their application would reduce the number of unnecessary radiographs by 30−40%.

Keypoint

Use of the Ottawa Ankle Rules is essential prior to x-ray following ankle sprain.