Lateral Ankle Sprain

Anatomy of a lateral ankle sprain

The ankle joint is composed of three bones:

• the tibia (the larger shin bone),
• the fibula (a thinner bone that runs along the outer back portion of the lower leg), and
• the talus, a foot bone that connects to the tibia and fibula to form the ankle joint.

The way the tibia and fibula cradle the talus creates a functional “mortise,” similar to a carpenter’s joint, which allows the talus to sit securely between them. This structure provides a strong base for force transfer during walking, running, and jumping. Stability at this joint is reinforced not just by bones, but by multiple ligaments and muscular attachments extending from the lower leg into the foot.

Lateral ankle sprains occur when the foot rolls inward, placing excessive tension on the lateral ligaments, the stabilizing structures on the outside of the ankle. Three key ligaments are involved:

• Anterior Talofibular Ligament (ATFL)
• Calcaneofibular Ligament (CFL)
• Posterior Talofibular Ligament (PTFL)

The ATFL is the most commonly injured ligament in lateral ankle sprains, affected in 90–95% of cases.¹ It’s especially vulnerable during plantarflexion (toes pointed downward) combined with inward rolling of the ankle. The CFL may also be involved, typically in moderate to severe sprains. MRI studies show approximately 41% of lateral ankle sprains injure both the ATFL and CFL.¹ The PTFL, located deeper and farther back, is much less likely to be injured, only seen in about 5% of lateral sprains.¹

Like most soft tissue injuries, lateral ankle sprains are graded based on severity:

• Grade I: Mild stretch or microscopic tearing of the ATFL. Minimal swelling and pain. Little or no loss of function or range of motion.¹³
• Grade II: Partial tear of the ATFL and possibly CFL. Noticeable swelling, bruising, and pain. Moderate difficulty bearing weight. Reduced range of motion.¹³
• Grade III: Full-thickness tear of ATFL and CFL, sometimes involving the PTFL. Severe swelling, inability to bear weight, and marked instability.¹³

Functional Impact on Athletes

The ankle joint plays a crucial role in propulsion, helping athletes push off during sprints, jumps, and rapid changes of direction. When ligaments become stretched or torn, the mechanical stability of the joint is compromised. This laxity (loss of tension and support) makes it more difficult to generate force, especially during high-velocity or side-to-side movements.

Beyond mechanical stability, these ligaments are also rich in mechanoreceptors, sensory nerve endings that help detect joint position and movement, a sense called proprioception. Damage to these structures doesn’t just affect strength and range of motion, it also disrupts the brain’s ability to know where the foot is in space.³ As a result, athletes with lateral ankle sprains often experience poor coordination during high-level movements, even after the pain has resolved. This impaired proprioception is a key reason why re-injury rates are so high if rehab is rushed or incomplete.

Cause of a lateral ankle sprain

Ankle sprains are the most common sports injury.^1,3,4 Sprains occur when the ankle moves into a combination of plantarflexion (like pressing down on the gas pedal) and inversion (turning the sole of your foot inward).^1,2,4 In the plantarflexed position, the talus bone moves to where it is not as supported in the mortise by the tibia and fibula, allowing the ankle to be more mobile but less stable. This is necessary for function but does put the ligaments (particularly the ATFL) on a stretch to maintain the joint’s stability. When this plantarflexed position is combined with the inversion motion, the ATFL and sometimes CFL are very stretched. Without any external force, this is fine and does not cause any issue. However, when running full speed, cutting, or landing, the force these ligaments take on may outweigh their ability, and injury can occur. 

60% of lateral ankle sprains occur due to direct trauma or contact.¹ In football, this happens when a player steps on another player’s foot, causing their foot to roll into that plantarflexed and inverted position, or it can occur when being rolled up with the toes stuck in the ground (laces down) and the shin moving forcefully toward the ground. The other 40% of injuries are non-contact, which often occurs to a misstep when cutting or landing and typically will occur when the athlete is fatigued.^5,6

Previous ankle sprains increase the risk for another sprain, with 29% suffering another ankle sprain within 12 months.^1,4 There are several factors to explain this. Consequences of an ankle sprain include loss of ROM, pain, laxity, loss of balance and proprioception (discussed above), and loss of strength in the entire limb up to the hip.⁴ All of these components are essential for athletic activity. Particularly the loss in proprioception and strength makes it harder for an athlete to be stable on one foot (running, cutting), leading to less coordination of the foot when it is pushing off and more likely to roll into the plantarflexion and inversion position leading to further injury. Because of this, a history of ankle sprains is often a predictor of future injury anywhere in that limb. 

Lateral ankle sprain rehab process

Unlike rehabbing from a high ankle sprain, a lateral ankle sprain is often an injury athletes can play through while rehabbing using external support such as taping or bracing. Because of this, there is no clear timeline for the rehab process; instead is based on progress.   

Early rehab will focus on reducing pain and inflammation through rest, ice, compression, elevation, and NSAIDs if needed. Depending on the grade of the injury, it may involve a period of wearing a boot and using crutches to offload the injury. Evidence supports early mobility and weight-bearing while wearing external support such as a boot or brace and crutches for grades I and II injuries. However, grade III injuries may need a period of time of immobilization and complete offloading, typically no more than ten days.²

For grades I and II, early weight-bearing with the use of external support help reduce swelling, restore ROM, prevent strength loss, and is correlated with a faster return to sport.² It is encouraged that weight-bearing be initiated as soon as is tolerable. Early ankle ROM exercises avoiding the inversion motion in the sitting or lying position are encouraged for grades I and II but may be delayed for grade III. For all grades, strength exercises on the table for the core, glutes, quads, and hamstrings are performed right away.  

As swelling and pain begin to subside, ROM exercises in all directions are performed and, when tolerable, can be progressed to strength exercises with a theraband.^1,2 When tolerable, beginning to exercise in the standing position and working on leg strength and balance exercises on differing surfaces (foam pad, Bosu ball, wobble board) is essential to regain the lost proprioception that is so important for high-level athletes.²

When pain and swelling are virtually gone, ROM, strength, balance, and proprioception are restored, the athlete can begin sport-specific training. This includes agility drills, plyometrics, running, cutting, jumping, and position-specific drills.  

Rehab Phases	Treatments	Criteria to Enter Phase
Early Phase	Rest, ice, compression, elevation, NSAIDs. Walking boot or brace and crutches as needed to allow tolerable weight bearing (possible casting for Grade III). Gentle ankle ROM in pain free ranges avoiding inversion. Table exercises for core, glutes, quads, hamstrings.	N/A first phase
Intermediate Phase	Ankle ROM exercises in all directions (if no pain), progress to theraband resistance. Seated ankle circles on BAPS board. When tolerable standing exercises (body squats, lunges, theraband walks). Balance and proprioception exercises starting on firm surface, progressing to unstable surfaces and single leg.	Minimal to no pain or swelling. Able to tolerate ankle ROM in all directions. Minimal to no pain with weight bearing.
Sport Specific	Full return to weight lifting. Agility drills, plyometrics, speed work, jumping. Position specific exercises.	No swelling. Pain free with weight bearing, running, jumping, cutting.

In a perfect world, the athlete will score adequately in a battery of tests before returning to the field. This includes strength testing of major lower body muscle groups, several different single-leg hop tests for speed, distance, and balance, and single-leg balance tests such as the Star Excursion Balance Test or the Y-balance test.² The research for lateral ankle sprains suggests that the injured leg shoulder score within 80-90% of the uninjured leg for a safe return to sport; however, a score above 95% is ideal.^1,2 With the pressures of competition, many athletes likely return to the field far before achieving the criteria on these tests, increasing their risk for re-injury. The use of external ankle bracing is often prescribed; in fact, some studies have shown it to reduce re-injury by up to 70%.⁷

References

1. D’Hooghe P, Crus F, Alkhelaifi K. Return to Play After a Lateral Ligament Ankle Sprain. Current Reviews in Musculoskeletal Medicine. 2020;13:281-288.
2. Halabchi F, Mohammad H. Acute ankle sprain in athletes: Clinical aspects and algorithmic approach. World J Orthop. 2020;11(12):534-558.
3. Houck J, Neville C, Chimentl R. The Foot and Ankle: Physical Therapy Patient Management Using Current Evidence. Current Concepts of Orthopaedic Physical Therapy. 2016(4).
4. Wilkstrom E, Mueller C, Cain MS. Lack of Consensus on Return-to-Sport Criteria Following Lateral Ankle Sprain: A Systematic Review of Expert Opinions. J Sport Rehabil. 2020;29(2):231-237.
5. Fong D, Leung WC, Mok KM, Yung P. Delayed anle muscle reaction time in female amateur footballers after the first 15 min of a simulated prolonged football protocol. J Esper Orthop. 2020;7:54.
6. de Noronha M, Kay ER, McPhee MR, Mnatzaganian G, Nunes GS. Ankle sprain has higher occurrence during the latter parts of matches: systematic review with meta-analysis. J Sport Rehabil. 2019;28:373-380.
7. Dizon JM, Reyes JJ. A systematic review on the effectiveness of external ankle supports in the prevention of inversion ankle sprains among elite and recreational players. J Sci Med Sport. 2010;13(3):309-317.