Peroneal Tendon Tears and Subluxation: The Lateral Ankle Problem Often Mistaken for a Sprain

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

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Anatomy and Function of the Peroneal Tendons

Two peroneal tendons travel together in a groove behind the fibula (lateral malleolus) held in place by the superior peroneal retinaculum — a strong band of tissue that acts as a seatbelt keeping the tendons in their groove. The peroneus brevis inserts on the fifth metatarsal base and everts the foot, while the peroneus longus wraps under the foot to the first metatarsal and stabilizes the arch during push-off.

These tendons serve as dynamic lateral ankle stabilizers, contracting reflexively during inversion perturbations to prevent ankle sprains. When the peroneal tendons are damaged or weakened, the ankle loses this dynamic protection, explaining why peroneal pathology and chronic ankle instability frequently coexist.

The tendons are vulnerable at several anatomical points: the retromalleolar groove behind the fibula where they change direction, the peroneal tubercle on the lateral calcaneus where the tendons diverge, and the cuboid tunnel where the peroneus longus turns under the foot. Each location has distinct injury mechanisms and clinical presentations.

Peroneus Brevis Tears

The peroneus brevis is the more commonly torn peroneal tendon, typically developing longitudinal split tears rather than complete ruptures. These tears occur as the tendon is compressed against the posterior fibula by the overlying peroneus longus during ankle inversion, creating a ‘nutcracker’ mechanism that progressively splits the tendon along its length.

Chronic lateral ankle pain that worsens with activity, particularly on uneven surfaces, is the hallmark presentation. The pain localizes behind and below the lateral malleolus, distinct from the anterior talofibular ligament location of typical ankle sprain pain. Patients often describe the feeling of lateral ankle ‘weakness’ or ‘giving way’ that mimics ligament instability.

A low-lying peroneus brevis muscle belly (extending into the retromalleolar groove) is a common anatomical variant that predisposes to tears by increasing volume within the confined retromalleolar space. MRI identifies this variant and helps surgical planning by showing the exact location and extent of tendon damage.

Peroneal Tendon Subluxation and Dislocation

Peroneal tendon subluxation occurs when the superior peroneal retinaculum tears or avulses from the fibula, allowing the tendons to slip out of their groove during ankle dorsiflexion and eversion. This commonly occurs during a forceful dorsiflexion-eversion injury — such as a skiing fall or aggressive cutting — but can be confused with a lateral ankle sprain.

Patients with subluxation describe a snapping or popping sensation behind the outer ankle, particularly with eversion or dorsiflexion. They may be able to voluntarily reproduce the subluxation. On examination, the tendons can often be seen and felt slipping over the fibular ridge with provocative maneuvers.

Acute retinacular tears have the best surgical outcomes when repaired within 2-3 weeks of injury. Unfortunately, most cases are misdiagnosed as ankle sprains, and the retinaculum heals in an incompetent position that allows chronic subluxation. Chronic subluxation requires surgical retinacular reconstruction combined with groove deepening for definitive correction.

Diagnostic Evaluation

Clinical examination includes palpation of the peroneal tendons from behind the fibula to their insertions, resisted eversion testing to assess strength and reproduce pain, the peroneal compression test (compressing the tendons against the fibula during circumduction), and subluxation provocation testing during active dorsiflexion-eversion.

MRI is the gold standard for evaluating peroneal tendon pathology. It reveals tendon tears (longitudinal splits, partial tears, complete ruptures), tenosynovitis (fluid surrounding the tendons within the sheath), retinacular integrity, and associated findings including lateral ankle ligament tears and bone marrow edema from associated injuries.

Dynamic ultrasound offers the unique advantage of real-time visualization during ankle motion. At Balance Foot & Ankle, Dr. Tom Biernacki uses ultrasound to observe tendon subluxation as it occurs during dorsiflexion-eversion, confirming the diagnosis when MRI shows equivocal findings. Ultrasound also guides diagnostic injections into the peroneal tendon sheath.

Conservative Treatment Approaches

Acute peroneal tendonitis and tenosynovitis often respond to immobilization in a CAM boot for 4-6 weeks, anti-inflammatory medication, and physical therapy focused on graduated peroneal strengthening and proprioceptive training. The boot eliminates the repetitive tendon motion that perpetuates inflammation while allowing controlled weight-bearing.

Lateral heel wedges and custom orthotics reduce peroneal tendon loading by slightly inverting the heel, shortening the moment arm through which the peroneals must work. For patients with chronic peroneal tendonitis associated with hindfoot valgus, correcting the valgus alignment through orthotic support can resolve tendon symptoms without surgical intervention.

Doctor Hoy’s Natural Pain Relief Gel applied along the course of the peroneal tendons behind the lateral ankle provides topical anti-inflammatory effect that complements systemic treatment and physical therapy. The cooling sensation and anti-inflammatory botanicals can reduce the post-activity soreness that limits rehabilitation progress.

Surgical Treatment Options

Peroneus brevis tendon debridement and tubularization repairs longitudinal split tears by removing the damaged tissue and resuturing the remaining healthy tendon into a cylindrical shape. When more than 50% of the tendon cross-section is damaged, tenodesis to the peroneus longus provides the mechanical strength that the damaged brevis can no longer provide.

Superior peroneal retinacular repair or reconstruction addresses subluxation. Direct repair is possible for acute injuries (within 2-3 weeks) where the retinaculum is reattached to the fibula. Chronic subluxation typically requires groove deepening — a procedure that creates a deeper channel in the posterior fibula — combined with retinacular reconstruction to prevent recurrence.

Recovery from peroneal tendon surgery involves 2-4 weeks of non-weight-bearing followed by progressive boot walking for 4-6 weeks. Physical therapy for peroneal strengthening and proprioceptive training begins after boot discontinuation. Return to full activity typically takes 3-4 months, with peroneal strength continuing to improve for up to 6 months.

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.