A snapping or popping sensation around the outer ankle during activity is a symptom that patients often dismiss as a “minor ankle problem” — and that providers frequently misdiagnose as a lateral ankle sprain. Peroneal tendon subluxation, however, is a mechanically distinct condition with specific anatomic pathology that does not respond to ankle sprain rehabilitation and frequently requires surgical correction for definitive resolution.

The Peroneal Tendons and Their Anatomy

The peroneus longus and peroneus brevis tendons run side-by-side behind the lateral malleolus (outer ankle bone), held in their groove by the superior peroneal retinaculum (SPR) — a fibrous band that acts as a pulley keeping the tendons against the fibula. The SPR is the critical structural element in peroneal tendon subluxation: when it tears or becomes incompetent, the tendons are free to sublux (snap) out of their groove and over the lateral malleolus.

How Subluxation Occurs

The classic mechanism is a sudden forceful dorsiflexion and eversion of the ankle — the same movement as catching a ski edge, landing from a jump, or a sudden directional change in sport. The peroneal muscles contract reflexively against the sudden load, the SPR cannot restrain the tendon force, and the retinaculum tears. Acute SPR tears produce swelling and ecchymosis around the posterolateral ankle that is easily mistaken for a lateral ankle sprain.

Chronic subluxation may also develop gradually in patients with a shallow peroneal groove in the fibula — an anatomic variant present in approximately 11% of the population — where even normal tensile loads cause intermittent subluxation without a discrete injury event.

Symptoms

The hallmark symptom is a visible or palpable snapping of the peroneal tendons over the lateral malleolus with ankle dorsiflexion and circumduction (circular ankle movement). Patients frequently demonstrate the subluxation themselves during the clinical examination. Associated symptoms include:

• Posterolateral ankle pain and swelling
• Sense of ankle instability or “giving way” with lateral movements
• Difficulty with uneven terrain and sport-specific cutting
• Tenderness directly over the posterior fibula

Diagnosis

The diagnosis is primarily clinical — a careful physical examination with provocative subluxation testing is highly sensitive. Diagnostic ultrasound provides real-time dynamic visualization of the subluxating tendon and evaluates for associated peroneal tendon tears (peroneus brevis longitudinal splits are common in chronic subluxation). MRI characterizes SPR integrity, groove morphology, and tendon quality when surgical planning requires comprehensive imaging.

Treatment

Acute SPR tear: Immobilization in a short leg cast for 6 weeks, followed by aggressive rehabilitation, can produce satisfactory outcomes in a proportion of patients — but recurrence rates with conservative treatment approach 50%. Athletes and active individuals typically benefit from early surgical repair to avoid recurrence and chronic instability.

Chronic subluxation: Conservative treatment rarely produces lasting resolution. Surgical SPR repair and retinaculum reconstruction — often combined with fibular groove deepening when the groove is shallow — is the definitive treatment. Peroneal tendon tears identified at the time of surgery are addressed simultaneously (debridement, tubularization, or tenodesis).

Recovery after surgical repair involves non-weight bearing for 3–4 weeks, boot walking for an additional 4 weeks, and return to sport at approximately 4 months with a brace.

Dr. Tom Biernacki, DPM

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Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.