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).
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.
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.
|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).
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.
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.
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.
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.
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).
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).
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:
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%.
Several fractures may occur at the time of injury, and can go unnoticed unless a thorough examination is carried out. Often these fractures only become apparent during rehabilitation when swelling begins to subside. It falls on the astute therapist to question why rehabilitation is not progressing normally and to refer for further investigation, which may include x ray, MRI or CT scan.
This is a fracture affecting either the lateral or medial malleolus. To palpation pain is located close to the malleolus itself rather than in the ligament tissue. The subject usually finds it difficult to bear weight in the clinic, and will not have been able to bear weight immediately after injury. Where the ankle mortice has been compromised, internal fixation is usually required. Hairline fractures, stable fractures and those affecting the posterior aspect of the malleolus and/or involving less than 25% of the articular surface are normally managed conservatively.
This is a spiral fracture of the fibula together with a tear of the distal tibiofibular syndesmosis and the interosseous membrane. The medial malleolus normally fractures and the deltoid ligament ruptures. The injury occurs only in high-impact activities and requires urgent surgical referral.
This fracture is more common in cases where ankle sprain has occurred in the presence of a compression force such as landing from a single leg jump. The talar dome is compressed within the ankle mortise and may fracture at the superomedial corner particularly. The condition is normally not recognized at the time of injury, but presents as a dull persistent ache during rehabilitation. There will be persistent swelling with stiffness. The site can be palpated by plantar flexing the ankle to draw the talar dome forwards of the ankle mortise. Injury may be graded from (I) focal compression of the subchondral bone through to (IV) fully detached bone fragment. Treatment is by reduced weight bearing while maintaining motion to stimulate cartilage healing (Karlsson, 2007). Occasionally arthroscopic removal of the bone fragment may be required.
The force which causes an acute lateral ligament injury is sometimes severe enough to pull (avulse) the peroneus brevis tendon away from its attachment to the 5th metatarsal. The avulsion fracture is usually treated conservatively.
The lateral aspect of the talus, which normally articulates with the fibula and calcaneus, may fracture. Pain occurs over the bone area which is palpated anterior and inferior to the tip of the lateral malleolus. If the fracture is not displaced, simple immobilization is required. Where displacement is greater than 2 mm excision or internal fixation is generally required (Karlsson, 2007).
The anterior calcaneal process is palpated anterior to the sinus tarsi. This area is normally not tender in cases of lateral ligament injury, but where fracture has occurred tenderness is exquisite. The fracture may not be revealed by x-ray and can require MRI or CT scan. Again immobilization is required unless the fragment is displaced in which case excision may be called for.
Immediate management consists of the PRICE protocol, with electrotherapy modalities as appropriate. Intermittent pneumatic compression (IPC) used in conjunction with cooling is effective. In the subacute phase, massage, especially finger kneading around the malleolus, is of value in preventing the development of pitting oedema. Transverse frictions may be used to encourage the development of a mobile scar, and may be used as a prelude to manipulation for scar tissue rupture in a chronic injury. Grade II and III injuries present with marked swelling and are protected non-weight bearing (severe injury) or preferably partial weight bearing with a compression bandage. Where minimal swelling indicates a grade I injury, an eversion strapping may be applied to protect the ligament from inversion stresses and to shorten it. A felt wedge is used beneath the heel to evert the subtaloid joint, and a U-shaped pad is placed over the submalleolar depressions to prevent pockets of oedema forming and to apply even compression when the ankle is strapped. Adhesive strapping is applied after skin preparation or underwrap, initially to lock the subtaloid joint and then to passively evert the foot. The athlete can then walk partial weight bearing in a well-supporting shoe.
Early mobility is essential to increase ligament strength and restore function. For grade I and II injuries, early mobilization has been shown to be more effective than immobilization. In a group of 82 patients with these grades of injury, 87% who were immobilized with a plastercast for 10 days still had pain after 3 weeks. This compared to 57% of those who received early mobilization in the form of an elastic strap for 2 days followed by a functional brace for 8 days (Eiff, Smith and Smith, 1994). Even grade III injuries (rupture) respond better to conservative treatment than surgery. Studies have shown 87% good and excellent results with conservative management compared to 60% for surgery of grade III injuries. In addition at 6 weeks post injury the surgical group had limited range of motion not seen in the conservative group (Kaikkonen, Kannus and Jarninen, 1996).