Orthopaedic Surgery - Ankle Sprain

Basics

An acute lateral ankle sprain is one of the most common injuries in sport and is also frequently encountered in the general population.

The injury usually involves the lateral ligament complex of the ankle. The anterior talofibular ligament (ATFL) is affected most often, either as a partial tear or complete rupture. More severe injuries may additionally involve the calcaneofibular ligament (CFL).

Most lateral ankle sprains occur through an inversion mechanism, often while the ankle is plantarflexed.

Classification

Lateral ankle sprains are commonly classified according to the degree of ligament injury.

Grade I injuries involve a partial tear or stretching of the lateral ligaments without major mechanical instability.

Grade II injuries involve a partial or complete tear of the ATFL together with partial injury of the CFL.

Grade III injuries represent complete rupture of both the ATFL and CFL and are generally associated with greater swelling, bruising, pain, and instability.

Sequence of Ligament Injury

As the severity of an inversion injury increases, the lateral stabilizing structures tend to fail in sequence.

The anterolateral joint capsule is generally injured first, followed by the ATFL.

With greater force, the injury may progress to involve the CFL.

This sequence explains why isolated ATFL injuries are more common than combined ATFL and CFL tears.

Anterior Talofibular Ligament

The ATFL is the most frequently injured ligament of the ankle.

It is the principal restraint to inversion when the ankle is in a plantarflexed position.

The ligament is particularly vulnerable when the foot is subjected to a combination of inversion, plantarflexion, and internal rotation.

Because many ankle sprains occur in this position, ATFL injury is extremely common.

Calcaneofibular Ligament

The CFL contributes to stability of both the ankle and subtalar joints.

It becomes particularly important in resisting inversion when the ankle is in a neutral or dorsiflexed position.

CFL injury therefore tends to occur when inversion forces are applied while the ankle is less plantarflexed.

Involvement of the CFL usually indicates a more severe sprain.

Dynamic Stabilizers

The peroneal muscles and tendons are the primary dynamic stabilizers resisting ankle inversion.

Rapid contraction of the peroneal muscles can help prevent excessive inversion and protect the lateral ligament complex.

Weakness, fatigue, or delayed neuromuscular response of the peroneals may increase the risk of recurrent sprains.

Epidemiology

Ankle sprains are among the most common musculoskeletal injuries.

In the United States, approximately 27,000 ankle sprains occur each day.

They are considered the most frequent athletic injury and occur particularly often in activities involving running, jumping, landing, and rapid changes in direction.

Risk Factors

Athletes are at increased risk because of repetitive loading and frequent changes in direction.

Dancers are also vulnerable because of repeated extreme ankle positions and balance demands.

Structural abnormalities such as congenital tarsal coalition may alter hindfoot mechanics and predispose to recurrent sprains.

A varus hindfoot alignment also increases the tendency for the ankle to invert and may contribute to repeated injury.

Etiology

The usual mechanism is inversion of the foot while body weight is transmitted through the ankle.

The degree of plantarflexion at the time of injury influences which ligament is most likely to be damaged.

Inversion in plantarflexion primarily stresses the ATFL, whereas inversion with the ankle closer to neutral or dorsiflexion places greater stress on the CFL.

Diagnosis

Signs and Symptoms

Patients commonly present with pain, tenderness, and swelling over the lateral aspect of the ankle.

Bruising may develop over the lateral malleolus and surrounding soft tissues.

Weight-bearing may be painful, and patients with more severe sprains may initially have considerable difficulty walking.

History

The mechanism of injury should be carefully established.

An inversion injury occurring with the ankle in plantarflexion is more suggestive of ATFL injury.

Inversion occurring with the ankle in dorsiflexion or near-neutral position places greater stress on the CFL.

The history should also determine whether the patient heard or felt a pop, was able to continue activity, and has sustained previous ankle sprains.

Physical Examination

Tenderness and swelling are usually localized to the lateral aspect of the ankle, particularly anterior and inferior to the tip of the lateral malleolus.

The degree of swelling and bruising should be documented.

The entire ankle and foot should be examined to ensure that an associated fracture or other injury is not overlooked.

Muscle Strength

Manual strength testing should include the major muscle groups acting across the ankle.

Particular attention should be given to the peroneal muscles and tendons, because they provide important dynamic resistance to inversion.

Pain, weakness, or loss of function may indicate associated tendon injury.

Neurovascular Examination

A complete neurovascular examination should be performed.

The superficial peroneal nerve can occasionally sustain a traction or stretching injury during an inversion sprain.

Sensation over the dorsum of the foot, motor function, pulses, and capillary refill should therefore be assessed.

Assessment of Ligament Stability

Mechanical stability should be evaluated once pain and swelling permit.

The injured ankle should always be compared with the contralateral side because a certain degree of physiologic laxity may be normal.

The main clinical tests are the anterior drawer test and inversion or talar tilt test.

Anterior Drawer Test

The anterior drawer test primarily assesses the ATFL.

The distal tibia is stabilized firmly with one hand while the other hand grasps the heel.

With the ankle in a neutral or slightly plantarflexed position, the heel and hindfoot are drawn anteriorly relative to the tibia.

Excessive anterior translation compared with the opposite side suggests ATFL insufficiency.

Inversion Tilt Test

The inversion tilt test primarily evaluates the CFL.

The ankle is positioned in neutral dorsiflexion.

The examiner stabilizes the distal tibia with one hand and applies an inversion force to the hindfoot with the other.

Excessive talar tilt or inversion compared with the uninjured ankle suggests CFL disruption.

Imaging

Plain Radiographs

When imaging is clinically indicated, standard ankle radiographs include anteroposterior, lateral, and mortise views.

Radiographs are primarily used to exclude associated fractures.

They may also demonstrate an osteochondral lesion of the talus, pre-existing arthritis, or another bony abnormality.

CT

Computed tomography is not routinely required for a straightforward ankle sprain.

CT may be useful when an occult fracture is suspected despite normal plain radiographs.

It may also assist in the assessment of a suspected tarsal coalition or other complex bony abnormality.

MRI

MRI is rarely necessary for an uncomplicated acute ankle sprain.

It may be appropriate when symptoms are unusually severe or persistent, or when an associated tendon tear, osteochondral injury, or other soft-tissue abnormality is suspected.

MRI provides detailed visualization of the ligaments, tendons, cartilage, and bone marrow.

Differential Diagnosis

Important differential diagnoses include a distal fibular fracture, osteochondral fracture of the talar dome, peroneal tendon subluxation, congenital tarsal coalition, talar fracture, and calcaneal fracture.

Persistent or atypical pain after an apparent ankle sprain should prompt reconsideration of these alternative diagnoses.

Treatment

General Measures

Most acute ankle sprains are treated nonoperatively.

Initial treatment commonly follows the RICE protocol: rest, ice, compression, and elevation.

These measures help reduce pain and swelling during the acute phase.

Prolonged complete immobilization is generally avoided when the injury is stable because early protected movement helps restore function.

Weight-Bearing

Weight-bearing can usually be advanced gradually as pain permits.

An ankle brace may provide support and allow earlier ambulation while limiting excessive inversion.

Patients with mild injuries can often progress rapidly, whereas more severe sprains may require a longer period of protected weight-bearing.

Ankle Bracing

A functional ankle brace can reduce painful motion while allowing controlled mobility.

Bracing is particularly useful during the early return to walking and athletic activity.

Continued brace use during high-risk sports may also reduce the likelihood of recurrent injury.

Range of Motion

Gentle active ankle movement should begin as tolerated.

Early range-of-motion exercises help reduce stiffness and improve circulation.

Patients may perform simple exercises such as drawing the alphabet with the great toe to encourage controlled multidirectional ankle movement.

Proprioceptive Training

For mild sprains, a home-based proprioceptive program may be sufficient.

Exercises may include single-leg balance activities, controlled ankle movements, and progressive balance challenges.

Proprioceptive retraining is important because ankle sprains can impair joint-position awareness and neuromuscular control.

Severe Sprains

More severe injuries may benefit from a formal physical therapy program.

Treatment should address swelling, mobility, muscle strength, endurance, balance, and proprioception.

The rehabilitation program should progress gradually toward running, jumping, cutting, and other sport-specific activities.

Activity Modification

Sporting activity should be restricted until pain and swelling have improved and ankle function has recovered.

Return to sport should not be based solely on the passage of time.

The patient should regain adequate strength, range of motion, balance, and confidence before resuming unrestricted activity.

Physical Therapy

Physical therapy should emphasize range of motion, strengthening, and proprioceptive retraining.

Both concentric and eccentric strengthening may be used, with particular attention to the peroneal muscles.

Balance-board exercises and single-leg activities can improve neuromuscular control and reduce the risk of recurrent sprains.

Medication

NSAIDs and simple analgesics may be used when pain is significant.

However, medication is often unnecessary for mild sprains.

Pain control should complement, rather than replace, functional rehabilitation.

Surgical Management

Surgical repair of an acute lateral ankle ligament tear is rarely necessary.

Most even high-grade sprains heal satisfactorily with appropriate nonoperative treatment and rehabilitation.

Primary repair of the ATFL and CFL may be considered only in selected acute situations.

Surgery for Recurrent Instability

Surgery may become appropriate when repeated sprains lead to chronic mechanical instability despite adequate rehabilitation and bracing.

Operative treatment may involve direct repair of the lateral ankle ligaments.

Reconstruction using tendon tissue, including part of the peroneus brevis tendon, has historically been used when direct repair is not feasible.

Follow-Up

Patients should be reviewed according to the severity of the injury and their functional demands.

Recovery should be assessed by evaluating pain, swelling, range of motion, strength, balance, and stability.

Persistent symptoms should prompt reassessment for an associated osteochondral, tendon, or bony injury.

Prognosis

The prognosis is excellent for most patients.

Recovery time varies according to the severity of the ligament injury.

Grade I sprains generally improve relatively quickly, whereas grade II and III injuries may require a longer period of rehabilitation before full athletic function returns.

Complications

Possible complications include an osteochondral lesion of the talus, recurrent ankle sprains, chronic instability, and ankle impingement.

Inadequate rehabilitation is an important contributor to recurrent symptoms.

Repeated sprains may eventually produce chronic ligamentous laxity, cartilage injury, and degenerative change.

Recurrent Sprains

A previous ankle sprain substantially increases the risk of another injury.

Residual weakness, impaired proprioception, ligamentous laxity, and premature return to sports all contribute to recurrence.

Structured rehabilitation and preventive bracing are therefore important after the initial injury.

Ankle Impingement

Repetitive injury may lead to scar formation, synovitis, osteophytes, or other tissue changes around the ankle.

These abnormalities can produce painful mechanical impingement during ankle movement.

Persistent pain or restricted motion after apparently successful treatment should therefore be investigated further.

Patient Monitoring

Patients should regain full or near-full strength and range of motion before returning to unrestricted sports.

They should also be able to perform functional activities such as running, jumping, cutting, and single-leg balance without pain or instability.

Functional bracing or taping during the return to athletics may help reduce the risk of recurrence, particularly in patients with a history of previous ankle sprains.