Ankle Injuries

The ankle is a complex joint that is capable of a wide range of movement. There is flexion, extension, inversion and eversion as well as a combination of movements. All this is necessary not just for locomotion but to traverse uneven ground. The ankle takes the full weight of the body and in running and jumping the forces that are exerted on it are considerable.

The history and following examination help to decide whether there has been a significant liklihood of an ankle fracture or foot fracture - always apply and document the Ottawa rules:

• How long ago was the injury?
• Ask about the precise mechanism of the injury. It is most often whilst crossing uneven ground or a sudden change of direction whilst playing sport. The patient will describe it as "rolling over" on the ankle. Check that this means an injury caused by excessive inversion. The injury may have resulted from jumping from a height.
• Was there any snap or popping sound? A snap may be a broken bone. A pop may be a ruptured ligament.
• Ask exactly where is the pain.
• What happened after? Was the patient able to get up and walk again quite soon? Did he need helping to walk? If it was a sports injury, was he able to continue?
• Ask about previous injury.

As always, be sensitive to the patient's response and do not try to force any examination that is obviously causing considerable distress. Examination of the uninjured ankle may give an indication of the normal range of movement and power:

• Did the patient walk in? If so, with how much discomfort and disability?
• Look at the ankle. It is distorted? There may be a swelling over and around the lateral malleolus, but does the basic anatomy look intact?
• Does any swelling or bruising look compatible with the mechanism of injury?
• If there is no obvious deformity, note any swelling or bruising and whether any effusion is present. This may be a fullness either side of achilles tendon.
• Palpate for crepitus and any tenderness, especially over the malleolar regions, over the anterior tibiofibular ligament, the whole length of the fibula, the base of the 5th metatarsal and check to see if calcaneal pressure elicits pain.
• Gently test all 6 different ranges of motion. These are:
  • Plantar flexion
  • Dorsiflexion
  • Inversion
  • Eversion
  • Inversion and eversion when plantar flexed
  • Inversion and eversion when dorsiflexed
• The normal range of inversion is about twice the range of eversion. Test muscle power by resisting these movements.
• The anterior draw test for inversion injuries is to assess the anterior ligament: With the ankle in a neutral position, grip the tibia with one hand and cup the heel with the other, pulling the foot forward. Displacement of >3 mm is abnormal.
• The side-to-side test for dorsiflexion injuries is to look for widening of the ankle mortise. With the foot in a neutral position, hold the tibia in one hand and heel in the other and stress from side to side. There may be pain or an audible clunk.
• The squeeze test involves squeezing the tibia and fibula together at mid calf. Pain is experienced more distally or in the ankle.
• Thompson's test is to assess if the Achilles tendon is intact. With the patient lying prone with the knee flexed to 90°, squeeze the mid calf and this should should produce a visible plantar flexion at the ankle (sensitivity 96%, specificity 93%). Some ability to actively dorsiflex can be achieved by soleus with a completely ruptured Achilles tendon.

Apply the Ottawa rules¹ to see whether an X-ray is indicated (see further reading link).

Ottawa rules

Clinically it may be very difficult to differentiate a fracture from a severe sprain without an x-ray unless there is obvious distortion or instability. The Ottawa rules¹ were introduced in 1992 to reduce the number of unnecessary x-rays whilst at the same time minimising the number of fractures missed. They are not perfect but they are validated and if a clinician applies the Ottawa rules, this is effective risk management by a respected protocol. Obtaining x-rays of every injured ankle will have a yield of less than 15%. The original work has been reproduced elsewhere and analysed by meta-analysis² and systematic review³ and it confirms a specificity of around 100% but a sensitivity of about 30 to 40% for fractures of the ankle. This implies a considerable reduction in the number of negative x-rays whilst failing to x-ray very few if any fractures. The Ottawa rules apply not just to Pott's fractures but to fractures of the forefoot too. The Ottawa rules also appear to be applicable to children.⁴ Not everyone has found that dissemination of the Ottawa rules reduces the number of x-rays, even in Canada.⁵

• Can the patient walk 4 steps immediately after the injury or when seen as an emergency?
• Check for localised tenderness at specific sites. These are the posterior edge or tip of both malleoli, the navicular, and the base of the fifth metatarsal.

This is based largely on the site of the pain and tenderness. There may be more than one injury:

• Lateral - Consider simple inversion sprain, fractured lateral malleolus, osteochondritis dissecans, peroneal tendon subluxation, Maisonneuve fracture, bifurcate ligament avulsion.
• Medial - Eversion sprain, fractured medial malleolus, tendon injury (flexor hallucis longus or posterior tibialis)
• Anterior - dorsiflexion sprain, anterior tibialis tendon injury, syndesmotic (high ankle) ligament sprain.
• Posterior - Achilles tendon injury, os trigonum fracture, calcaneal fracture.
• Sole of foot - 5th metatarsal fracture.

Usually investigations require nothing more sophisticated than a plain x-ray. The indications to x-ray or not are discussed under the Ottawa rules. X-rays will show fracture and significant bony displacement but not damage to ligaments. Here MRI may be needed.⁶

• Simple sprains - lateral sprains are more common and can be treated conservatively. Simple medial sprains can also be treated conservatively, but tenderness over the deltoid ligament, with or without laxity associated with fractures or instability may require fixation.
• Syndesmosis (high ankle) sprain - the syndesmotic ligaments are the combination of the interosseus ligament and lower tibulofibular ligaments which normally stabilises the mortise joint and fixes the fibula in the fibular notch. Look for widening of the mortise (tib-fib gap should be <5mm measured 1cm above the joint line on AP and Mortise views) - stress x-rays may be needed. Squeeze test, side to side and forced external rotation both cause pain at the syndesmosis. Healing takes longer than standard lateral sprains, and may require internal fixation if there is associated fibular fracture.
• Lateral malleolar (fibular) fracture - stable fracture: symptomatic treatment only (bandage or POP). Always look for medial widening of the mortise (>4 mm) which indicates an unstable fracture (associated deltoid ligament injury) and may need fixation.
• Medial malleolar fracture - undisplaced stable fractures can be treated with POP. Unstable or displaced fractures, or bimalleolar fractures may need internal fixation. Posterior malleolar fracture may need fixation if >25% of articular surface involved (termed 'trimalleolar' or 'Cotton' fracture when accompanied by fractures of medial and lateral malleolus).
• Maisonneuve fracture - proximal fibular fracture caused by forced external rotation (eversion injuries). Tibial fracture needs no treatment, but examination under anaesthesia may be necessary to assess ankle instability - syndesmosis may need repair with one or sometimes two screws.
• Fractured distal epiphysis of tibia (Salter-Harris classification is normally used). Mild forms just need manipulation, more severe forms need open reduction and fixation.
• Fractured fifth metatarsal base - usually an avulsion fracture caused by sudden inversion. Conservative treatment is usually all that is required.
• Jones fracture - occurs distal to the inter-metatarsal joint which is seen in athletes (may be treated by POP or may need fixation).
• Injury to posterior tubercle of talus or the nearby Os trigonum (accessory ossicle located just posterior to it present in around 10%) - resulting from severe plantar flexion (eg in dancers, runners and footballers) - produces pain posterior to lateral malleolus, particularly on forced plantar flexion (eversion against resistance is pain free). POP or steroid injection may help.
• Achilles tendon rupture - Test continuity with Thompson test. Management either equinus plaster or surgical repair.

Neurological disease or other causes of a poor gait may predispose to ankle injuries but a very common condition that is easy to overlook is flat feet. A flat foot will cause hyperpronation and a degree of eversion of the ankle. This may predispose to pain from poor posture and ankle and other injuries. Correction of the fallen arch will improve gait and reduce injury.