A lateral ankle sprain is an injury to the ligaments on the outer side of your ankle, caused when your foot rolls inward. It is the single most common injury in sports, accounting for about 15% of all athletic injuries, and it affects roughly 2 per 1,000 people in the general population each year. The injury ranges from a mild stretch to a complete tear, and what you do in the first days afterward has a major impact on whether the ankle heals fully or becomes a recurring problem.
Which Ligaments Are Involved
Three ligaments run along the outside of your ankle, connecting your lower leg bone (the fibula) to the bones of your foot. Together they form the lateral ligament complex, and they are weaker than the ligaments on the inner side of the ankle, which is why outward-side injuries are so much more common.
The first and most frequently injured is the anterior talofibular ligament (ATFL), which connects the fibula to the talus bone at the front of the ankle. The second is the calcaneofibular ligament (CFL), which runs from the fibula down to the heel bone. The third, the posterior talofibular ligament (PTFL), attaches the fibula to the back of the talus. In a typical lateral sprain, the ATFL tears first. More forceful injuries also damage the CFL, and only the most severe sprains involve all three.
How It Happens
A lateral ankle sprain occurs when your foot rolls inward while your lower leg stays in place or rotates outward. This combination puts extreme stress on the outer ligaments. It most often happens right after your heel strikes the ground during walking or running, or when you land from a jump on an uneven surface or on another person’s foot. Landing with your toes pointed downward increases the risk because it places the ATFL in its most vulnerable position.
People with naturally high arches or feet that tend to roll outward are more susceptible. Their foot structure shifts more weight to the outer edge of the foot, creating a mechanical disadvantage that makes it easier for the ankle to give way. A previous sprain is also a major risk factor, because damaged ligaments and reduced balance awareness make repeat injuries more likely.
Who Gets Them Most Often
Ankle sprains peak in adolescence and young adulthood. Males between 15 and 19 have the highest rate at about 8.9 per 1,000 person-years, while females peak earlier, between ages 10 and 14, at 5.4 per 1,000 person-years. Sports with frequent jumping, cutting, and physical contact carry the greatest risk. Basketball, volleyball, soccer, and football consistently top the list.
Grades of Severity
Lateral ankle sprains are classified into three grades based on how much ligament damage has occurred.
- Grade 1: The ligament is stretched or has a slight tear. You’ll notice mild tenderness, some swelling, and stiffness, but the ankle feels stable. Walking is usually possible with minimal pain.
- Grade 2: The ligament is partially torn. Swelling, pain, and bruising are more noticeable, and the injured area is tender to touch. The ankle may feel somewhat stable, but walking is painful.
- Grade 3: One or more ligaments are completely torn. Swelling and bruising are severe, the ankle feels unstable or gives out under your weight, and walking is typically not possible due to intense pain.
A doctor can usually determine the grade based on how much swelling, bruising, and pain you have, along with simple physical tests that check whether the ankle joint moves more than it should.
How Doctors Rule Out a Fracture
Not every ankle injury needs an X-ray. Clinicians use a set of guidelines called the Ottawa Ankle Rules to decide. An X-ray is recommended if you are 55 or older, if you can’t take four steps both right after the injury and at the doctor’s office, or if there is tenderness directly over the bone at the back or tip of either ankle bone. X-rays of the midfoot are recommended if there’s tenderness at the base of the fifth metatarsal (the bony bump on the outer edge of your foot), the cuboid, or the navicular bone. If none of these criteria apply, the injury is very likely a sprain rather than a fracture.
Lateral Sprain vs. High Ankle Sprain
A standard lateral sprain and a high ankle sprain (also called a syndesmotic sprain) involve different structures and feel different. In a lateral sprain, swelling appears below and in front of the outer ankle bone, and tenderness is concentrated over the ATFL and CFL. In a high ankle sprain, the injury affects the ligaments that hold the two lower leg bones together above the ankle joint. Swelling and tenderness appear higher up the leg, above the ankle, and can extend upward along the space between the two shin bones. High ankle sprains typically take longer to heal and are more common in sports that involve rotational forces on a planted foot.
Early Treatment: Why Movement Matters
The traditional advice for a sprained ankle was complete rest, but current evidence supports a different approach. The POLICE protocol, which stands for Protection, Optimal Loading, Ice, Compression, and Elevation, has replaced the older PRICE method (which called for strict rest). The key difference is “optimal loading,” meaning you begin gentle, pain-free movement and weight-bearing early rather than immobilizing the ankle entirely.
This shift matters for outcomes. In a clinical comparison, patients who followed the POLICE protocol recovered faster, returned to work sooner, and had significantly fewer repeat sprains than those who rested completely. The group that rested had over five times the rate of recurrent sprains. Early mobilization, kept within a pain-free range, appears to stimulate healing without causing further damage.
In practical terms, this means protecting the ankle with a brace or tape, applying ice and compression to manage swelling, keeping the ankle elevated, and beginning gentle weight-bearing and range-of-motion exercises as soon as you can do so without sharp pain.
Rehabilitation and Preventing Reinjury
Beyond the first few days, rehabilitation focuses on restoring strength, flexibility, and something less obvious: proprioception, your ankle’s ability to sense its own position. A sprain damages not only the ligament fibers but also the nerve endings within them that tell your brain where your foot is in space. This is why a previously sprained ankle feels “wobbly” or unreliable even after the pain is gone.
Balance training directly targets this problem. Exercises include standing on one leg with your eyes closed, using a wobble board, and balancing on one foot while catching or throwing a ball. These drills retrain the communication between your ankle and brain so you can react faster to an unexpected roll. People with a history of ankle sprains who completed proprioceptive training programs had a 36% reduction in the risk of spraining the ankle again. For every 13 people who did these exercises, one additional repeat sprain was prevented.
This type of training works for people who have never sprained an ankle too, reducing first-time sprain rates in athletic populations. A few minutes of balance work several times per week is one of the most effective preventive measures available.
The Risk of Chronic Instability
About 20% of people who sprain their ankle go on to develop chronic ankle instability, a condition where the ankle repeatedly gives way during everyday activities or sports. This can happen because the ligaments healed in a lengthened position and no longer hold the joint tightly, because the nerve damage from the original sprain was never addressed with balance training, or both.
Chronic instability leads to a cycle of repeated sprains, each one causing further ligament damage and increasing the likelihood of the next. Over time, this can contribute to cartilage damage within the joint. The strongest protection against this outcome is completing a full rehabilitation program after the initial sprain rather than stopping once the pain fades. Pain resolves well before the ligament and nerve function have fully recovered, which is why many people return to activity too early and end up reinjuring the same ankle.