The Snapping Ankle (Peroneal Subluxation)
Injury and damage to the peroneal tendons can present in many forms, from tendinitis and tenosynovitis to subluxations and dislocations to even tears and ruptures. Although a very infrequent occurrence in the lower extremity, the diagnosis of peroneal subluxation (sometimes referred to as snapping ankle or popping peroneal syndrome) can often be missed. Because it occurs most often among athletes, it is commonly misdiagnosed as an ankle sprain (1,3). Therefore, it is important to recognize and treat it early to prevent further, more chronic, conditions from resulting.
There are two peroneal muscles in the lateral (outside) aspect of the leg: the peroneus longus and the peroneus brevis. Both muscles start in the lower leg, course down the lateral side of the leg and ankle, where they become tendinous and then travel behind the lateral malleolus (the bony bump along the outside of the ankle). The peroneus brevis tendon then inserts into the base of the 5th metatarsal bone, while the peroneus longus tendon continues underneath the foot and inserts on the plantar side of the 1st metatarsal base and medial cuneiform.
These muscle act to plantarflex the ankle and evert (move outwards) the foot. The peroneus longus muscle also helps stabilize the medial column of the foot when standing.
Another important structure involved with the peroneal tendons is the superior peroneal retinaculum (SPR), which is a band of tissue that holds the tendons against the ankle, preventing them from subluxing or dislocating.
The Snapping Ankle (Peroneal Tendon Subluxation & Dislocation)
Causes of Subluxation & Dislocation:
Peroneal dislocations (complete displacement) and subluxations (partial dislocations) most often occur among athletes. Because of the quick movements required in certain sports, certain motions can put acute and significant stress on the peroneal tendons, thus resulting in rupture of the SPR and dislocation of the tendons (3).
Abnormal anatomy can also put an athlete at increased risk for peroneal subluxation. For example, if there is weakness in the SPR or the fibular groove that the tendons sit in is shallow, these anomalies can also put the tendons at increased risk for displacement (2).
If the condition is chronic, the person may be able to describe having a clicking or popping sensation around the lateral ankle. Similar symptoms can be reproduced with certain movements of the ankle.
In the acute setting, diagnosing the subluxation may be more difficult because it can often present similarly to an ankle sprain with pain, swelling, and bruising around the lateral aspect of the ankle (2). Therefore, it is essential for physicians to be thorough with their examination to pinpoint the exact area of pain. Typically, with peroneal syndromes, the pain will be slightly behind the fibula bone. The pain and subluxation may also be reproduced with certain movements and tests of the ankle (1).
X-rays can be ordered to help rule-out an ankle fracture or other bony injury or abnormality. Unfortunately, they do not show soft tissue, though, so they are not much help with diagnosing peroneal tendon subluxations.
An MRI or ultrasound may be more helpful in detailing soft tissue pathology; however, an MRI will not pick up the subluxation or dislocation if the tendon is not displacement during the time of the exam and an ultrasound takes an experienced professional to know how to use the machine and how to maneuver the foot and ankle to reproduce the displacement while capturing the image (1).
Conservative treatment with cast immobilization can be attempted for certain cases. The goal is to allow the SPR to scar back down to the fibula (2); however, failure rates have been documented as high as 76% (3). Therefore, surgical intervention is often recommended, especially for athletes and recurrent dislocations (3).
There are several different surgical treatment options available for subluxations and dislocations. They range from reattachment and/or reinforcement of the SPR to bone block procedures, fibular groove deepening procedures to prevent recurrent subluxation, and even re-routing of the tendons (2,3).
Regardless of the procedure, associated anatomic and biomechanical abnormalities should also be addressed at the time of surgery to prevent recurrence.
Peroneal subluxation is most common among athletes but still remains an uncommonly reported injury. For physicians, it is important to keep it in the list of differential diagnoses when an athlete presents with symptoms around the lateral ankle because early recognition and treatment is key to preventing long-term complications.
DISCLAIMER: The above information is meant for educational purposes only and should not be construed as medical advice. Please consult the doctor, or your own healthcare professional, should you have questions or concerns, related to your health.
1. Chauhan, Y.A., Miller, J.M. (2017). How To Diagnose And Treat Subluxing Peroneal Tendons In The Athlete. Podiatry Today, 30(1), 50-55. Retrieved from https://www.podiatrytoday.com/how-diagnose-and-treat-subluxing-peroneal-tendons-athlete
2. Peroneal tendon subluxation. Physiopedia. Retrieved from https://www.physio-pedia.com/Peroneal_tendon_subluxation
3. van Dijk, P. A., Gianakos, A. L., Kerkhoffs, G. M., & Kennedy, J. G. (2016). Return to sports and clinical outcomes in patients treated for peroneal tendon dislocation: a systematic review. Knee Surgery, Sports Traumatology, Arthroscopy, 24(4), 1155-1164.
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