Lateral Ankle Sprain

Etiology

• Lateral ankle sprains are one of the most common injuries in sports. Roughly one ankle sprain per 10,000 person-days occurs worldwide, resulting in about 2-million acute ankle sprains every year in the United States alone. Studies in both the US and European countries have shown that 30% of all athletic injuries involve ankle sprains. Of studies that have documented ankle sprains, injuries to the lateral ankle account for 85% of all ankle sprains (1).

Anatomy Review

The image above is from Netter's Anatomy

• The lateral ligamentous complex of the ankle consists of three ligaments: anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (1).

• ATFL: is a flat ligament that blends with the anterior lateral capsule of the ankle. It originates at the distal anterior fibula and inserts on the body of the talus just anterior to the articular facet (1).

• PTFL: originates from the medial surface of the lateral malleolus and courses medially in a horizontal manner to the lateral and posterior aspect of the talus. The ligament is confluent with the joint capsule and is well vascularized by vessels going to the talus and the fibula via the digital fossa (1).

• CFL: is a cordlike ligament that originates from the anterior border of the distal lateral malleolus just below the origin of the ATFL. The ligament courses medially, posteriorly, and inferiorly from its fibular origin to the calcaneal insertion. The CFL is confluent with the peroneal tendon sheat, just as the ATFL blends with the anterior capsule of the ankle joint (1).

Biomechanics

• In dorsiflexion, the ATFL is loose, whereas the CFL is taut. In plantar flexion the converse occurs: the ATFL is taut, and the CFL becomes loose. The PTFL is maximally stressed in the dorsiflexed position (1).

• In biomechanical studies, the ATFL has a lower load to failure than the CFL. Conversely, the ATFL is capable of undergoing the greatest strain compared with the CFL and PTFL. Thus, the ATFL can undergo the greatest deformation before failure and allows internal rotation of the talus during plantar flexion. However, its lower maximum load to failure, along with the common mechanism of injury of plantarflexion and inversion, helps explain the greater frequency of injuries to the ATFL (1).

• According to several studies, the ATFL functions primarily in restricting the internal rotation of the talus. When the ankle is plantarflexed, the ATFL also limits adduction. When the ankle is in an anatomically neutral position, the ATFL lies almost horizontal (1).

• The CFL primarily prohibits adduction and acts almost independently in the neutral and dorsiflexed positions. In plantarflexion, it restricts adduction in conjunction with the ATFL (1).

• The PTFL prevents external rotation with the ankle in a dorsiflexed position. Once the ATFL has ruptured the short fibers of the PTFL also have a role in restricting internal rotation (1).

Pathogenesis

• The most common ligament disruption by far is the ATFL. The second most common injury is a combination rupture of the ATFL and CFL. Isolated tears of the CFL are uncommon but can occur. Even less common are combination tears of the ATFL, CFL, and PTFL. Isolated injuries to the PTFL and isolated combinations of CFL and PTFL are exceedingly rare (1).

• Various injuries are noted in association with lateral ligamentous sprains: partial or complete tears of the peroneus longus and brevis tendons, chondral fractures of the talus, osteochondral fracture in the talocrural joint, medial ligamentous injuries, syndesmotic injuries, and bifurcate ligament injuries. Displaced or non-displaced avulsion fractures of the fifth metatarsal and calcaneocuboid compression injuries or ligament avulsions have also been noted (1).

• Although complete nerve disruption has not been reported, it is common to see post-sprain neuritis of the sural nerve, superficial peroneal nerve, deep peroneal nerve, or posterior tibial nerve (1).

Clinical Presentation

• Patients with a lateral ankle sprain often describe a popping or tearing sensation in the ankle and occasionally an audible noise (1).

• The injuries occur during running, cutting, or while landing from a jump (1).

• Patients will typically describe an inversion, plantarflexion, or internal rotation mechanism of injury (1).

• Swelling and pain occur immediately after the injury (1).

• Many athletes give a history of multiple ankle sprains (1).

• Patients who have more severe injuries will typically have difficulty with weight-bearing (1).

• The range of motion of the ankle is limited in dorsiflexion, plantar flexion, and inversion (1).

• An anterior drawer maneuver often elicits pain, however, those with a complete rupture might have less pain than those with a partial rupture (1).

• Inversion stress of the calcaneus typically induces pain or demonstrates instability in patients with calcaneofibular disruption (1).

• In a relaxed patient with a complete ATFL tear, anterior subluxation of the talus may be appreciated, and a suction sign is usually apparent at the anterolateral joint (1).

Image from: Mann's Surgery of the Foot and Ankle Volume 2, Chapter 30

Classification Systems

Anatomic System (2)

• Grade I: ATFL sprain

• Grade II: ATFL and CFL sprains

• Grade III: ATFL, CFL, and PTFL sprains

AMA Standard Nomenclature System (3)

• Grade 1: Ligament stretched

• Grade 2: Ligament partially torn

• Grade 3: Ligament completely torn

Clinical System (4)

• Mild sprain: minimal functional loss, no limp, minimal or no swelling, point tenderness, pain with the reproduction of mechanism of injury.

• Moderate sprain: moderate functional loss, unable to rise on toes or hop on the injured ankle, limp when walking, localized swelling, point tenderness.

• Severe sprain: diffuse tenderness and swelling; patient prefers to crutch for ambulation.

Special Tests:

Anterior drawer test

Image from: https://us.humankinetics.com/blogs/excerpt/injury-recognition-ankle-tests

• Procedure: Stabilize tibia, hold the foot in 20 PF, pull the talus forward, and compare to other side

• Positive test: if pain and excessive anterior movement of the talus on the lateral side (ATF tear) or on both sides (ATF and CF)

• Sensitivity: 74%, Specificity: 38%, +LR: 1.19, -LR: .68 (5).

Talar tilt:

Image from: slideshare.net

• Procedure: Stabilize the lower leg, ankle in neutral, tilt calcaneus into adduction (varus), and compare to other side.

• Positive test: Excessive motion or pain.

• The sensitivity of the inversion talar tilt is reported to be 50% to 52%, with specificity for detecting combined ATFL and CFL sprains of 68% and 88% (6).

Board Questions:

A 23-year-old basketball player complains of pain on the outside of his ankle after landing from a jump. Upon examination, the patient has is walking with a limp, complaints of moderate functional limitations, point tenderness, and localized swelling. What level of injury do you suspect?

1. Mild

2. Moderate

3. Severe

4. Surgical

A 16-year-old baseball player reports twisting his ankle after stepping on a teammate's foot. The patient reports immediate pain and swelling after suffering this injury. Which of the following ligaments would MOST likely be involved?

1. Calcaneofibular

2. Posterior tiobiotalar

3. Anterior talofibular

4. Anterior tibiotalar

Answers

1. A moderate sprain would be the correct answer. As listed above in the clinical system classification states that a moderate sprain includes moderate functional loss, unable to rise on toes or hop on the injured ankle, limp when walking, localized swelling, point tenderness.

2. The anterior talofibular ligament would be the correct answer. As listed above the anterior talofibular ligament is the most commonly injured ligament in the lateral ankle complex. The anterior tibiotalar ligament is on the medial side and is one of the four ligaments that make up the deltoid ligament.

References

1. Mann's Surgery of the Foot and Ankle, Ed. 9, Volume 2, Chapter 30: Athletic Injuries to the Soft Tissues of the Foot and Ankle.

2. Baxter DE: Traumatic injuries to the soft tissues of the foot and ankle: In Mann RA, editor: Surgery of the Foot and ANkle, ed 5, St. Louis (MO), 1986, CV Mosby, pp 456-472.

3. Standard nomenclature of athletic injures. In Report of the Committee on the Medical Aspects of Sports, Chicago, 1966, American Medical Association.

4. Jackson DW, Ashley RL, Powell JW: Ankle sprains in young athletes: relation of severity and disability, Clin Orthop Relat Res 101:201-215, 1974

5. Croy et al., 2013

6. Larkins, Lindsay & Baker, Russell & Baker, Jayme. (2020). Physical Examination of the Ankle: A Review of the Original Orthopedic Special Test Description and Scientific Validity of Common Tests for Ankle Examination. Archives of Rehabilitation Research and Clinical Translation. 2. 100072. 10.1016/j.arrct.2020.100072.