What Is Peroneal Tendon Subluxation?

Peroneal tendon subluxation occurs when the peroneus brevis and peroneus longus tendons slip out of the fibular groove — the bony groove on the posterior aspect of the lateral malleolus that normally holds the tendons in position — and displace anteriorly over the lateral malleolus with dorsiflexion and eversion movements. The superior peroneal retinaculum (SPR) is the fibrous band that holds the tendons in the groove; SPR injury allows the tendons to sublux. Peroneal subluxation produces a palpable and often audible snap or pop at the outer ankle — frequently confused with a lateral ankle sprain and missed in acute ankle injury evaluations. At Balance Foot & Ankle in Howell and Bloomfield Hills, Michigan, Dr. Tom Biernacki, DPM evaluates peroneal tendon subluxation. Call (810) 206-1402.

How Peroneal Subluxation Occurs — Mechanism and Risk Factors

The SPR is torn during a sudden forceful dorsiflexion with peroneal muscle contraction — the exact mechanism of a skiing fall (when the boot prevents ankle inversion but the ski tip catches and creates dorsiflexion force). Peroneal subluxation is among the most common skiing injuries, occurring in 0.3–0.5% of ski season injuries. It also occurs in football, basketball, and any sport with sudden direction changes. Anatomic risk factors: a shallow or convex fibular groove (normally concave) — present in 11% of the population, creating an inherently unstable tendon bed; and peroneus quartus muscle (an accessory muscle present in 10–22% of the population that crowds the fibular groove). MRI identifies groove depth and any concurrent peroneal tendon tears.

Diagnosis — The Subluxation Provocation Test

The clinical diagnosis of peroneal subluxation: the subluxation provocation test — the examiner passively dorsiflexes and everts the foot while palpating the posterior fibular groove; tenderness at the posterior fibular groove and visible or palpable tendon displacement anterior to the fibula confirms subluxation; and dynamic ultrasound — real-time imaging during the provocation maneuver directly visualizes the tendons subluxing out of the groove, providing definitive diagnostic confirmation without MRI. MRI is ordered to assess SPR integrity, fibular groove depth, and concurrent peroneal tendon tears (30–40% of peroneal subluxation cases have associated longitudinal tendon tears). X-ray shows a “fleck sign” — a small avulsion fracture of the posterior fibular rim where the SPR avulses — in 15–50% of acute cases.

Conservative Management for Acute SPR Injury

Acute peroneal subluxation (within 6 weeks of injury, first episode) can be trialed conservatively: 6 weeks non-weight-bearing in a cast with the foot in plantarflexion and slight inversion — this position reduces the peroneal tendon displacement and allows SPR healing in a shortened position. Conservative treatment success rate: 50% for acute injury in cast; much lower for chronic recurrent subluxation. The patient population most appropriate for conservative trial: first-episode acute injury in a non-athlete or low-demand patient. Athletes and patients with recurrent subluxation are better served by early surgical intervention to avoid the chronic tendon damage and groove deformity that develops from repeated subluxation episodes.

Surgical Management — SPR Repair and Groove Deepening

Surgical management provides the most reliable outcome for peroneal subluxation in athletes and chronic cases: SPR repair with reattachment to the posterior fibula (primary repair for acute tears with intact tissue); fibular groove deepening osteoplasty (creating or deepening the fibular groove to mechanically constrain the tendons) — combined with SPR repair for patients with anatomically shallow grooves; and concurrent peroneal tendon tear repair when present. Recovery: 6–8 weeks non-weight-bearing, 3–4 months to full sports return. Published return-to-sport rates exceed 90% with surgical management. Long-term subluxation without repair creates progressive tendon wear — the tendons repeatedly abrade over the fibular rim with each episode, creating the longitudinal tears that require more extensive surgical management.

Peroneal Tendon Subluxation Management in Howell & Bloomfield Hills Michigan

Dr. Tom Biernacki, DPM evaluates peroneal subluxation with the subluxation provocation test, dynamic ultrasound, and MRI coordination at Balance Foot & Ankle. Same-day evaluation available for acute skiing and sports injuries. Serving Howell, Brighton, Ypsilanti, Bloomfield Hills, Troy, Auburn Hills, and all Southeast Michigan. Book your evaluation or call (810) 206-1402.

Your Board-Certified Podiatrists

Dr. Tom Biernacki, DPM

Board-Certified · FACFAS

Dr. Carl Jay, DPM

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Dr. Daria Gutkin, DPM

Podiatrist

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.