Ankle sprain

An ankle sprain is an injury to one or more of the ligaments that stabilise the ankle joint. In athletes, and in runners in particular, the most common form is the lateral ankle sprain, usually caused by a sudden inversion movement of the foot combined with internal rotation. It mainly involves the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL) and, more rarely, the posterior talofibular ligament (PTFL).

But not all ankle sprains are lateral sprains: medial sprains, tibiofibular syndesmosis sprains, osteochondral lesions, associated fractures and tendon injuries must also be recognised. A “sprain” is therefore a diagnosis of ligament injury, but its location and severity must be precisely determined.

Ankle sprain is one of the most common sports injuries and is often considered minor. Yet a significant proportion of athletes are left, after a first sprain, with a feeling of instability, reduced mobility, loss of strength, proprioceptive deficits, apprehension or recurrent episodes: an inadequately rehabilitated sprain can thus progress to chronic ankle instability. The problem is therefore not only to make the pain go away, but to regain an ankle that can bear load, control, react, accelerate, change direction and run on uneven ground.

The ankle is made up mainly of the lower end of the tibia, the lower end of the fibula and the talus. The tibia and fibula form a true clamp around the talus, the tibiofibular mortise, which mainly allows dorsiflexion and plantar flexion movements — although ankle function cannot be separated from that of the subtalar joint, the midfoot and the foot.

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The lateral ligaments

The lateral ligament complex comprises three main ligaments. The anterior talofibular ligament is the most frequently injured, being particularly stressed during inversion, plantar flexion and rapid foot movements. The calcaneofibular ligament contributes more to lateral stability when the foot is in a neutral position and is often involved in more severe sprains. The posterior talofibular ligament is much stronger and rarely injured in isolation; its rupture generally indicates a severe sprain.

The medial ligament and the syndesmosis

The medial ligament, or deltoid ligament, stabilises the inner side of the ankle. Much more robust than the lateral ligaments, it is injured less often, but medial sprains should be taken seriously because they may be associated with a fracture, a syndesmosis injury or significant instability. The tibiofibular syndesmosis — the anterior and posterior inferior tibiofibular ligaments and the interosseous membrane — maintains the relationship between the tibia and fibula above the ankle; an injury to it is a syndesmosis sprain (“high ankle sprain”), which generally takes longer to recover from than a simple lateral sprain.

Classic mechanism

The classic mechanism of a lateral sprain combines inversion, internal rotation and plantar flexion: the foot suddenly turns inwards while the body weight continues to move forward, placing particular stress on the anterior talofibular ligament. This mechanism can occur on landing, when running on uneven ground, during a change of direction, or after placing the foot on the outer edge of an irregularity in the ground. In road runners, sprains often occur on an uneven patch, after a misstep or when very fatigued; in trail runners, the situations are more varied (roots, stones, side slopes, technical descents, wet ground, neuromuscular fatigue) — the risk increasing as the ability to react quickly decreases.

After a first sprain, several factors may persist — ligament laxity, proprioceptive deficit, reduced peroneal strength, reduced mobility, impaired postural control, apprehension — making the athlete more vulnerable to a new perturbation: sprain → deficit → instability → new sprain → worsened deficit.

Ankle sprain is one of the most common sports injuries across all sports, and frequently affects both road runners and trail runners. A significant proportion of athletes are left with residual instability after a first sprain, which explains how common recurrences and chronic ankle instability are in the absence of appropriate rehabilitation.

The classic mechanism of a lateral sprain combines inversion, internal rotation and plantar flexion, usually occurring on landing, when running on uneven ground or during a change of direction.

Risk factors for recurrence

After a first sprain, residual ligament laxity, a proprioceptive deficit, reduced peroneal strength, reduced mobility, impaired postural control or apprehension may persist and predispose to a further sprain. Patients often return to sport as soon as the pain disappears, even though they may still have deficits in strength, balance, mobility or reaction: the disappearance of pain is therefore only one stage of recovery.

Terrain and fatigue factors

In road runners, sprains often occur on an uneven patch of ground, after a misstep or when very fatigued. In trail runners, the situations are more varied: roots, stones, side slopes, technical descents, wet ground. Neuromuscular fatigue reduces control capacity and increases the risk of a wrong movement.

Symptoms depend on severity and generally include pain, swelling, difficulty walking, bruising, limited mobility and a feeling of instability. Pain is usually greatest around the injured ligament; in a lateral sprain, it is located around and slightly in front of the lateral malleolus.

Swelling often appears quickly and may be localised or diffuse; very rapid and massive swelling may indicate intra-articular bleeding or a significant injury, but its extent alone does not allow the severity of the ligament injury to be precisely determined. Bruising may appear in the following hours or days and gradually spread down towards the outer edge of the foot, the heel or the sole, without this migration meaning that the injury is getting worse. In a significant sprain, weight-bearing can be very painful, with limping or walking on the inner edge of the foot; an inability to walk should prompt a search for a fracture, in particular using the Ottawa rules (malleolar pain combined with tenderness on palpation of the posterior edge or tip of the malleolus, or inability to take four steps both immediately after the injury and at the time of assessment).

Clinical examination

The examination should answer several questions: is there a fracture? which ligament is probably injured? is there instability or an associated injury? what is the patient’s functional level and when will they be able to return to running? Systematic palpation looks for tenderness over the anterior talofibular ligament, the calcaneofibular ligament, the malleoli, the base of the 5^th metatarsal, the navicular, the syndesmosis and the talus — bone tenderness should raise the possibility of a fracture.

The anterior drawer test mainly assesses the stability of the anterior talofibular ligament (forward translation of the talus relative to the tibia) and is generally more informative a few days after the injury, once the acute pain and swelling subside. The talar tilt test (forced varus) assesses lateral stability, in particular the calcaneofibular ligament. Pain above the joint should prompt a search for syndesmosis involvement (squeeze test, external rotation stress test). Examination of the peroneal tendons (pain behind the lateral malleolus, pain on resisted eversion, weakness, subluxation) and assessment of dorsiflexion (Weight-Bearing Lunge Test) complete the examination. Once the acute phase has passed, functional assessment (single-leg balance, calf raise, squat, jumping, running, changes of direction) allows a gradual shift from anatomical examination to function and then to sport.

The vast majority of acute lateral sprains are treated without surgery; a complete ligament rupture visible on MRI (for example of the anterior talofibular ligament) is not in itself a systematic indication — surgery should not be decided on this basis alone. It may be discussed in cases of persistent chronic instability, failure of properly conducted rehabilitation, a significant ligament injury with instability, an osteochondral lesion requiring treatment, certain syndesmosis injuries or particular associated injuries.

In some cases of chronic instability, reconstruction or repair of the lateral ligaments may be offered, aiming to restore mechanical stability, confidence and function — but it should generally be combined with a full postoperative rehabilitation programme.

Recovery time depends enormously on severity: a mild sprain may require a few weeks to return to normal activity, a moderate sprain often requires several weeks of sports recovery, a severe sprain may require several weeks to several months, and a syndesmosis sprain can take a particularly long time to recover. These timeframes are only a guide: functional recovery matters more than the number of days elapsed, and two runners with a sprain of similar grade can progress very differently.

Return to sport follows the international PAASS framework, which recommends assessing five domains rather than time elapsed alone: Pain (pain during sport and over the last 24 hours), Ankle impairments (mobility, strength, endurance, power), Athlete perception (confidence, feeling of stability), Sensorimotor control (proprioception, dynamic balance) and Sport/functional performance (jumps, agility, sport-specific movements, full training). Persistent pain after several weeks is not necessarily abnormal — ligaments heal gradually, and swelling, mobility, strength or proprioception may remain impaired for some time — but a lack of gradual improvement should lead to the diagnosis being reassessed.

Preventing recurrence should be considered an integral part of treatment. It is based on strengthening (peroneals, triceps surae, intrinsic foot muscles, proximal chain), proprioception (single-leg balance, perturbations, jumps, fast reactions) and sport-specific work (changes of direction, uneven terrain, side slopes, descents) — proprioceptive and neuromuscular exercise programmes playing an important role in preventing recurrence. Managing fatigue is also essential, as it reduces neuromuscular control and increases the risk of a wrong movement.

For trail runners, it is particularly useful to work on single-leg balance, lateral jumps, landing, moving over uneven terrain and control on descents, so that the foot is able to react even before the runner is aware of the unevenness of the ground.