Ankle injuries and sprains

See also the separate Ankle Fractures article.

Ankle sprains and injuries are common in primary care, A&E and sports medicine¹ . Most are inversion and plantar flexion injuries that lead to damage to the lateral ligaments² .

The ankle is a complex joint which is capable of a wide range of movement: flexion, extension, inversion and eversion as well as a combination of these movements. This allows locomotion and balance on both level and uneven ground. The ankle takes the full weight of the body and is subject to considerable force, particularly in running and jumping.

Many ankle injuries are managed conservatively. However, obvious clinical deformity (ie dislocation) or injuries with neurovascular compromise of the foot are an orthopaedic emergency for which immediate reduction is required (see 'Management' section, below).

Between 50% and 70% of people who sustain a lateral ankle sprain will develop chronic ankle instability, which is characterised by lingering pain, instability, injury recurrence, and persistent functional disability³ .

Anatomy of the ankle joint²

Two joints allow movement of the ankle:

• The true ankle joint (tibiotalar joint) - articulation is between the lower end of the tibia, the malleoli and the body of the talus. This joint allows dorsiflexion and plantar flexion of the ankle.

• The subtalar joint - articulation is between the talus and calcaneus. This joint allows inversion and eversion of the ankle.

The distal tibia has a prominent medial malleolus and a less prominent posterior malleolus. The distal fibula is known as the lateral malleolus. The joint capsule and the surrounding ligaments stabilise the ankle. The distal fibula is joined to the distal tibia by the anterior and posterior inferior tibiofibular ligaments, an inferior transverse ligament and a syndesmosis ligament. The anterior and posterior talofibular ligaments join the fibula to the talus. The talus is joined to the calcaneus by the calcaneo-fibular ligament. The deltoid ligament joins the medial malleolus to the talus, calcaneus and navicular bones.

Joints of the ankle and foot

By OpenStax College, Anatomy & Physiology, Connexions Website, Jun 19, 2013, via Wikimedia Commons⁴

Assessment of ankle injuries

Initial assessment should follow the principles for any trauma:

• Carry out a primary survey following the 'ABCDE' principles of resuscitation and trauma care.

• Assess clinically for obvious deformity and for neurovascular status. If there is neurovascular compromise or dislocation (obvious deformity) of the joint, the fracture should be reduced immediately under analgesia or sedation.

• Displaced fractures should be reduced as soon as possible after initial assessment - this reduces pain/swelling and may prevent skin necrosis.

History and examination help to decide whether there has been a significant likelihood of an ankle fracture or foot fracture. Apply and document the Ottawa Rules^{5 6} .

History

• Ask how long ago the ankle injury occurred.

• Mechanism of injury: injuries are most often whilst crossing uneven ground or after a sudden change of direction whilst playing sport:

  • Was there excessive inversion or eversion? The injury may have resulted from jumping from a height.

  • Was there a 'snap' sound? (This does not differentiate between a sprain and a fracture² .)

  • Where is the pain felt?

  • What happened afterwards? Was the patient able to weight bear immediately? Did they need help to walk? If it was a sports injury, were they able to continue?

  • Was there immediate swelling? (Immediate swelling is due to bleeding and suggests significant tissue injury.)

• Previous ankle injury: establish whether there is underlying weakness or instability in the ankle and whether an old fracture might be evident on X-ray.

• Past medical history - eg, osteoporosis or metabolic bone disease.

• Drug history - eg, long-term corticosteroid use.

Examination²

• Inspection:
  

  • Note whether the patient walked in and, if they did, with how much discomfort and disability.

  • Look at the ankle and whether there is obvious deformity.

  • Note whether there is swelling or bruising and whether it looks compatible with the mechanism of injury.

  • Establish whether an effusion is present. This may be a fullness either side of the Achilles tendon.

  • Look for any open wounds.

• Palpation:
  

  • Palpate for crepitus and tenderness, especially over the malleolar regions, over the anterior tibiofibular ligament, the whole length of the fibula and the base of the fifth metatarsal. Note whether calcaneal pressure elicits pain.

• Examine for neurovascular injury:
  

  • Assessment of neurovascular status is by sensation over the dorsal and plantar surfaces of the foot, measuring capillary refill in all digits and palpating the distal pulses (the dorsalis pedis artery is absent in 2-3% of the population). Vascular compromise is the urgent concern in dislocations and fracture-dislocations. Sural nerve and peroneal nerve palsies are a rare complication of severe sprains.

• Movement/power:
  

  • These cannot be tested in most cases as the joint may be swollen, painful, fractured or dislocated.

• Examine for co-existing injuries:
  

  • Pay special attention to the ipsilateral knee and foot.

  • Check for tenderness (fracture) of the proximal fibula.

• Specific tests (if appropriate and tolerable to the patient) include:
  

  • Thompson's test: this is to assess if the Achilles tendon is intact. With the patient lying prone with the knee flexed to 90°, squeeze the posterior calf muscles - this should produce a visible plantar flexion at the ankle if the tendon is intact.

  • The anterior drawer test: this can show excessive anterior displacement of the talus on to the tibia. If the anterior talofibular ligament is torn, the talus will subluxate anteriorly compared with the unaffected ankle. With the ankle in a neutral position, stabilise the leg over the distal tibia with one hand and cup the heel with the other, pulling the foot forward. The patient should be relaxed and both legs compared. A positive sign is a greater anterior movement on the injured side, with the injured side having more movement than the uninjured.

  • The talar tilt test (also called the inversion stress test): this stresses the calcaneo-fibular ligament. This test is not usually feasible in acute injuries, owing to swelling; however, it may be used to assess stability during healing. With the foot in a neutral position, hold the lower leg in one hand and the heel in the other: invert the ankle. Compare with the other leg.

  • Tests for syndesmosis injury:

    • Squeeze test: involves squeezing the tibia and fibula together at the mid calf. If pain is experienced more distally or in the ankle, this is a positive test.

    • Interosseous membrane tenderness test: this also looks for syndesmosis injury. Position the patient supine. Palpate between the tibia and fibular from the ankle proximally. Note the length of tenderness.

    • External rotation stress test: externally rotate and then passively dorsiflex the ankle. Pain at the syndesmosis is a positive test.

• Examination of the uninjured ankle may give an indication of the normal range of movement and power.

Investigations

The first question is often how to rule out ankle fracture, particularly where there is difficulty in weight bearing.

Ankle X-rays: Ottawa Rules^{6 7}

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 Ankle Rules were introduced in 1992 as a guideline with which to reduce costs and waiting times when ruling out serious ankle and midfoot fractures in the non-athletic, adult population.

Ankle radiography is indicated only if a patient has pain in the malleolar zone and any of the following findings:

• Bone tenderness at the posterior edge or tip of the medial or lateral malleolus, or

• Inability to bear weight (four steps) immediately after injury and at the time of assessment.

Foot radiography is indicated only if a patient has pain in the midfoot zone and any of the following findings:

• Bone tenderness at the base of the fifth metatarsal or over the navicular bone (located on the top inner side of the middle of the foot) or

• Inability to bear weight (four steps) immediately after injury and at the time of assessment.

The Buffalo Rule was derived to increase the diagnostic accuracy of the Ottawa Ankle Rules, with the point tenderness criterion directed to the crest or midportion of the malleoli (distal 6 cm of the fibula and tibia), reducing the likelihood of palpating over injured ligament structures⁷ .

Assessment of the Ottawa Ankle Rules suggests that they are valid in children, and they are in widespread clinical use, as they massively reduce costs and unnecessary X-ray exposure⁸ .

Imaging

• If an X-ray is performed, anteroposterior (AP), lateral and mortise views can be taken. For the mortise view, the foot is rotated about 15° internally. This allows a better view of the ankle mortise.

• If one injury is seen on X-ray, always look for a second.

• CT and MRI scanning are sometimes needed for fracture diagnosis and assessment of ligamentous or intra-articular injuries.

Ankle fracture diagnosis

The diagnosis and management of ankle fracture is covered in the separate Ankle Fractures article.

Ankle sprain diagnosis⁹

• The ankle and knee are commonly affected.

• The severity of symptoms and signs depends on the severity of the sprain (for example, whether there has been a partial or complete ligament tear). Common symptoms and signs include:

  • Tenderness and swelling.

  • Bruising.

  • Functional loss (for example, pain on weight-bearing).

  • Mechanical instability (if the sprain is severe).

  • Marked bruising and swelling, which may indicate a complete ligament tear or fracture.

Ankle muscle strain diagnosis⁹

There is commonly confusion between the terms sprain and strain. A strain includes inflammation of muscles and tendons. A sprain is a ligament injury.

• The clinical features of a muscle strain depend on the severity of the injury and the nature of the haematoma.

• There may be a history of a strain or 'pulled muscle'.

• Pain occurs in the affected muscle.

• Large haematomas can occur as a result of tearing of the intramuscular blood vessels.

• There may be obvious swelling, although small haematomas or those deep within the muscle are more difficult to diagnose clinically.

• Muscle function may be affected, depending on the severity of the strain.

Differential diagnosis

Commonly missed ankle/foot fractures are² :

• Proximal fibula.

• Base of fifth metatarsal (also a common site for stress fractures).

• Talus - dome, lateral process (Snowboarder's fracture) or posterior process.

• Tibial plafond.

Other causes of acute ankle pain are:

• Achilles tendon injury or Achilles tendinopathy.

• Joint pathology - eg, gout, osteochondritis dissecans.

• Tendon injury - eg, flexor hallucis longus, posterior tibialis or anterior tibialis tendon injuries; peroneal tendon subluxation.

• Stress fractures.

• Anterior process fracture of the calcaneus.

Ankle sprains - classification²

Lateral ankle sprains

These account for 85% of all ankle sprains, most commonly due to inversion of the plantar flexed foot¹⁰ .

Ankle sprains are classified from grade I to grade III depending on their severity:

• Grade I injuries - the ligament is stretched, with microscopic (but not macroscopic) tearing. Swelling is mild, with little or no functional loss and no joint instability. The patient bears weight at least partially.

• Grade II injuries - the ligament is stretched with partial tearing. Swelling is moderate-to-severe, with ecchymosis.There is moderate functional loss and mild-to-moderate joint instability. Patients usually have difficulty bearing weight.

• Grade III injuries - the ligament is completely ruptured. Swelling is immediate and severe, with ecchymosis. The patient usually cannot bear weight (or not without severe pain). There is moderate-to-severe instability of the joint.

Syndesmotic (high ankle) sprain
This is caused by dorsiflexion and eversion of the ankle with internal rotation of the tibia - eg, during skiing or football. The syndesmotic ligaments are the combination of the interosseous ligament and lower tibiofibular ligaments which normally stabilise the mortise joint and fix the fibula in the fibular notch.

• Look for widening of the mortise (tibiofibular gap should be <5 mm measured 1 cm above the joint line on AP and mortise views).

• Squeeze test, side-to-side test and forced external rotation all cause pain at the syndesmosis.

• Healing takes longer than standard lateral sprains - consider the diagnosis in those with continuing pain more than six weeks after the original injury.

Treatment and management of ankle sprains^{9 10 11}

• Treatment aim is to minimise discomfort and restore function. Most ligament injuries heal well, although there may be scarring.

• Functional support is generally preferable to immobilisation, unless the injury is severe. This means the use of a variable or immovable immobilising device in conjunction with exercise.

• Lateral sprains are most 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.

One overview of systematic reviews found that¹² :

• For the treatment of acute ankle sprain, there is strong evidence for non-steroidal anti-inflammatory drugs and early mobilisation, with moderate evidence supporting exercise and manual therapy techniques, for pain, swelling and function.

• Exercise therapy and bracing are supported in the prevention of chronic ankle instability.

Treatment for the first 72 hours

Protection, rest, ice, compression and elevation (PRICE)

• Protect from further injury (for example, by a tubular support bandage, ankle tape, brace or high-top high-lace shoes ¹³ ).

• Rest the ankle joint for 48-72 hours following injury. Consider the use of crutches in this period. In most cases, early controlled weight-bearing with the ankle well supported is preferable to complete rest.

• Ice should be applied as soon as possible after injury, for 10-30 minutes. (Less than 10 minutes has little effect. More than 30 minutes may damage the skin.) Do not put ice directly next to skin, as it may cause ice burn. This may limit pain, inflammation and bruising. Some doctors recommend re-applying for 15 minutes every two hours (during daytime) for the first 48-72 hours. Do not leave ice on while asleep.

• Compression with a bandage will limit swelling.

• Elevation aims to limit and reduce any swelling.

Avoidance of heat, alcohol, running and massage (HARM)

• Heat - which encourages blood flow which will tend to increase bruising and inflammation.

• Alcohol, which can increase bleeding and swelling and decrease healing.

• Running, which may cause further damage.

• Massage, which may increase bleeding and swelling.

Other treatment

• Analgesia if required.

• For simple sprains which are not severe, begin flexibility (range of motion) exercises as soon as they can be tolerated without excessive pain.

• For severe sprains (type III) a short period of immobilisation can result in quicker recovery. A short period of immobilisation in a below-knee cast or pneumatic brace may speed recovery compared to a compression bandage alone^{14 15} .

• Treatment of syndesmotic sprains may involve a fracture boot, short leg cast or non-weight bearing. Internal fixation may be required if the joint is unstable. See the separate Ankle Fractures article.

• Rarely, if ligaments are badly torn or the joint unstable, surgical repair may be indicated.

• Physiotherapy may be helpful in restoration to a full range of normal movement, improving the strength of the surrounding muscles and improving proprioception.

• Avoidance of sport or vigorous exercise involving the ankle for at least 3-4 weeks after a sprain.

Rehabilitation after ankle sprain

• After injury, full rehabilitation to build up the muscles around the joint is important; weak muscles can predispose to further injury. Guided rehabilitation over a period of weeks is recommended² .

• Athletes with severe sprains may need an ankle orthosis for several months following the injury² .

• Chronic ankle instability may follow an acute lateral ankle sprain. Initial treatment involves bracing or neuromuscular training. However, if symptoms persist, surgery may be considered¹⁶ .

• After a sprain, persistent symptoms remain in up to 30% of individuals¹⁰ .

Prevention of ankle sprain

Prevention of ankle sprains may be facilitated by wearing walking boots that protect the ankle (rather than shoes) when hiking over hills or uneven ground, or for manual labour.

Management of muscle strain

• Immobilise the injured muscle for the first few days after the injury. Consider the use of crutches in severe injuries.

• Start active mobilisation after a few days if the person has pain-free use of the muscle in basic movements and the injured muscle can stretch as much as the healthy contralateral muscle.

Dr Mary Lowth is an author or the original author of this leaflet.