Peroneal Tendon Subluxation: The Ankle Injury That Gets Misdiagnosed as a Simple Sprain

Written by Dr. Cory Calendine, MD | Board-Certified Orthopedic Surgeon | Bone and Joint Institute of Tennessee

TLDR: Peroneal tendon subluxation happens when the tendons on the outer side of your ankle slip out of their normal groove behind the fibula. This condition is frequently mistaken for a common ankle sprain because the symptoms overlap significantly. The pain, swelling, and bruising look almost identical. But the treatments are very different, and missing this diagnosis can lead to chronic ankle problems, tendon damage, and recurring instability. If your ankle sprain is not getting better with rest and physical therapy, peroneal tendon subluxation may be the real issue.

What Is Peroneal Tendon Subluxation?

Two tendons called the peroneus longus and peroneus brevis run along the outer side of your ankle, tucked into a groove behind the bony bump known as the lateral malleolus (the outside of the fibula). These tendons help you push your foot down and outward. They also play a critical role in stabilizing your ankle on uneven ground.

A tough band of tissue called the superior peroneal retinaculum (SPR) holds these tendons in place. Think of it like a seatbelt keeping the tendons locked in their groove. When the SPR gets torn, stretched, or pulled away from the bone, those tendons can slip out of position. That slipping is called subluxation. If the tendons move completely out of the groove, that is a full dislocation.

Peroneal subluxations account for roughly 0.3% to 0.5% of all traumatic ankle injuries. That number sounds small, but the real percentage is likely higher because so many of these injuries get labeled as simple ankle sprains.

Why Does Peroneal Tendon Subluxation Get Misdiagnosed?

This is one of the most commonly missed diagnoses I see in my practice. Patients come in after an ankle injury with swelling and bruising on the outer side of the ankle. The initial exam looks like a textbook lateral ligament sprain. And here is the tricky part: research shows that up to 78% of patients with SPR injuries also have damage to the lateral ankle ligaments at the same time. So the ligament injury is real, but it is not the whole story.

Overlapping Symptoms

Both conditions cause pain, swelling, and tenderness around the outside of the ankle. Both can happen during the same type of twisting injury. A patient who rolls an ankle playing basketball or catches a ski tip in the snow can tear the lateral ligaments and damage the peroneal retinaculum in a single event.

The Key Clinical Difference

The location of pain is the biggest clue. Lateral ligament sprains cause pain in front of and below the lateral malleolus. Peroneal tendon problems cause pain behind the lateral malleolus. That distinction matters, but swelling can make it hard to pinpoint the exact location early on.

Patients with peroneal tendon subluxation often describe a snapping or popping sensation when they move their ankle. They may notice it most while climbing or going down stairs. Some patients can actually see the tendons rolling over the bone on the outside of their ankle. That visual finding, when present, is a strong diagnostic indicator.

What Causes Peroneal Tendon Subluxation?

The most common mechanism involves forceful dorsiflexion (the ankle bending upward) combined with a sudden, strong contraction of the peroneal muscles. Skiing injuries are a classic example. When your ski tips dig into the snow and your body keeps moving forward, the ankle gets forced into dorsiflexion while the peroneal muscles fire hard to stabilize the foot. That combination of forces can strip the retinaculum right off the bone.

Risk Factors That Increase Your Chances

Your anatomy can make you more or less prone to this injury. A shallow or convex fibular groove gives the tendons less room to sit securely. Studies have found that 13 out of 14 patients in one surgical series had a convex peroneal groove instead of the normal concave shape. Other risk factors include a loose or thin retinaculum, heel valgus (a heel that tilts outward), and having a low-lying peroneus brevis muscle belly that creates extra bulk behind the fibula.

Athletes in sports that involve quick direction changes, jumping, and ankle dorsiflexion are at higher risk. Skiing tops the list, but ice skating, gymnastics, rugby, soccer, and basketball all produce this injury pattern.

How Is Peroneal Tendon Subluxation Diagnosed?

Physical examination is the starting point. I test for subluxation by having the patient dorsiflex and evert the foot against resistance. If the tendons visibly or palpably snap over the fibula, the diagnosis is straightforward. But here is an important point: a negative test does not rule out the condition. In chronic cases, patients may not be able to reproduce the subluxation on demand.

Imaging Studies

MRI is useful for looking at the static anatomy of the peroneal tendons, the retinaculum, the fibular groove shape, and any associated tendon tears. The Oden classification system describes four types of SPR injury. Type I, which is the most common by far, involves the retinaculum stripping away from the fibula along with the periosteum, creating a false pouch where the tendons can slip underneath.

Dynamic ultrasound has become increasingly popular because it lets us watch the tendons move in real time. Research has shown ultrasound to be 100% sensitive and 90% specific for peroneal subluxation, compared to just 23% sensitivity for MRI. That difference makes sense when you consider that MRI captures a single moment, while subluxation is a dynamic problem.

One study by Raikin et al. also identified a subgroup of patients with intrasheath subluxation, where the two peroneal tendons switch positions within the groove while the retinaculum stays intact. These patients had painful clicking behind the fibula but no visible subluxation on exam. Dynamic ultrasound was the key to making the diagnosis.

Treatment Options for Peroneal Tendon Subluxation

Conservative Treatment

For acute injuries caught early, non-surgical treatment may work. This typically involves placing the ankle in a cast or boot for four to six weeks to allow the retinaculum to heal back onto the fibula. The goal is to keep the tendons in their proper position while scar tissue forms and reattaches the retinaculum.

Here is what I tell my patients: conservative treatment has a role, especially for first-time acute injuries. But the success rate is not as high as we would like, particularly in active people. Many patients, especially younger athletes, end up with recurrent subluxation after conservative management. Once the tendons start slipping repeatedly, they develop damage over time, including tendinosis and longitudinal tears of the peroneus brevis tendon.

Surgical Treatment

When conservative treatment fails or the subluxation is chronic, surgery is usually the best path forward. The specific procedure depends on what we find during the operation.

The most common approach is repair of the superior peroneal retinaculum, often combined with deepening of the fibular groove. Groove deepening gives the tendons a better channel to sit in and reduces the chance of recurrence. If we find tendon tears during surgery, those are repaired at the same time. In cases where lateral ankle ligament instability coexists, that gets addressed in the same procedure.

Surgical outcomes are reliably excellent. One study showed average AOFAS ankle scores improved from 61 points before surgery to 93 points after, with pain levels dropping from 6.8 to 1.2 on a 10-point scale. Nine out of fourteen patients rated their result as excellent. The prognosis allows recreational and professional athletes to return to their preinjury level of performance.

When Should You See a Doctor About Lateral Ankle Pain?

See a specialist if you experience:

• Ankle pain behind the outer ankle bone that does not improve after six weeks
• A snapping or popping sensation when you move your foot
• Visible rolling of tendons over the outer ankle
• Repeated ankle sprains despite rehab and bracing
• Weakness or instability on uneven surfaces
• An ankle sprain that was treated properly but never fully healed

A thorough evaluation by an orthopedic surgeon who understands peroneal tendon pathology can make the difference between years of frustration and a clear diagnosis with a treatment plan that works.

Orthopedic Ankle Care in Franklin, Brentwood, and Nashville, Tennessee

If you are dealing with chronic lateral ankle pain or a sprain that just will not heal, getting the right diagnosis is the first step toward recovery. Dr. Cory Calendine specializes in musculoskeletal conditions at the Bone and Joint Institute of Tennessee, serving patients throughout Franklin, Brentwood, Nashville, and the greater Middle Tennessee area. Contact our office to schedule a consultation and find out if peroneal tendon subluxation could be the cause of your persistent ankle problems.

Medical Disclaimer: This information is for educational purposes only and should not replace professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider before making any decisions about your health or medical conditions. Individual results may vary based on personal health circumstances.

About the Author

Dr. Cory Calendine is a board-certified orthopedic surgeon specializing in joint replacement and musculoskeletal care at the Bone and Joint Institute of Tennessee, affiliated with Williamson Health. With years of clinical experience treating complex orthopedic conditions, Dr. Calendine is committed to providing evidence-based, patient-centered care to the Middle Tennessee community.

Frequently Asked Questions

How do I know if I have peroneal tendon subluxation or a regular ankle sprain?

The biggest difference is pain location. Ankle sprains cause pain in front of and below the outer ankle bone. Peroneal tendon subluxation causes pain behind the outer ankle bone. A snapping or popping sensation during ankle movement is another strong indicator of tendon subluxation rather than a simple sprain.

Can peroneal tendon subluxation heal on its own without surgery?

Acute injuries caught early can sometimes heal with immobilization in a cast or boot for four to six weeks. But success rates with conservative treatment are lower in active patients, and recurrence is common. Chronic or recurrent subluxation typically requires surgical repair.

What happens if peroneal tendon subluxation goes untreated?

Untreated subluxation leads to repeated episodes of the tendons slipping out of position. Over time, this causes progressive tendon damage, including tendinosis and longitudinal tears. The ankle becomes increasingly unstable and painful, and the tendon damage can become more difficult to repair.

How long is recovery after peroneal tendon subluxation surgery?

Recovery typically involves two weeks of non-weight-bearing in a cast, followed by four or more weeks in a walking boot. Physical therapy begins after immobilization and focuses on range of motion, strength, and proprioception. Most athletes return to full activity in three to four months.

Is peroneal tendon subluxation common in athletes?

Peroneal subluxation is most commonly associated with skiing but also occurs in ice skating, gymnastics, rugby, soccer, and basketball. Any sport involving sudden ankle dorsiflexion, quick direction changes, or forceful peroneal muscle contraction can produce this injury.

References:

• Raikin SM, Elias I, Nazarian LN. Intrasheath subluxation of the peroneal tendons. J Bone Joint Surg Am. 2008;90(5):992-999.
• Rosenberg ZS, Bencardino J, Astion D, et al. MRI Features of Chronic Injuries of the Superior Peroneal Retinaculum. AJR. 2003;181:1551-1557.
• Oden RR. Tendon injuries about the ankle resulting from skiing. Clin Orthop. 1987;216:63-69.
• Roth JA, Taylor WC, Whalen J. Peroneal tendon subluxation: the other lateral ankle injury. Br J Sports Med. 2010;44(14):1047-1053.
• Bodor D. Peroneal Tendon Dislocation and Superior Peroneal Retinaculum Injury. MRI Web Clinic. Radsource. October 2006.