Peroneal Tendon Tear & Tendinopathy: Lateral Ankle Pain Beyond Sprains

Persistent lateral ankle pain that doesn’t resolve after a typical ankle sprain recovery period is often attributed to “chronic instability” — but a significant number of these patients have peroneal tendon pathology that has been missed. The peroneal tendons (peroneus longus and peroneus brevis) run together behind the lateral ankle in a shared fibro-osseous tunnel, evert the foot, and provide crucial dynamic lateral ankle stability. Tears and tendinopathy in these structures are frequently underdiagnosed but highly treatable with the right approach.

Anatomy and Function of the Peroneal Tendons

Two peroneal muscles originate in the lateral lower leg:

• Peroneus brevis: Inserts on the base of the fifth metatarsal. Everts the foot and stabilizes the lateral ankle.
• Peroneus longus: Crosses under the foot and inserts on the medial cuneiform and first metatarsal base. Plantarflexes the first ray and maintains the transverse arch.

Both tendons travel together in a groove behind the fibula (the lateral ankle bone), held in place by the superior peroneal retinaculum. This groove is the site of most pathology.

Types of Peroneal Tendon Pathology

Peroneal Tendinopathy (Overuse)

Degeneration of the tendon tissue from repetitive overload — common in runners, dancers, and court sports athletes. Symptoms: chronic aching lateral ankle pain, worsened by activity, improved with rest. Tenderness directly over the tendons behind the fibula.

Peroneus Brevis Longitudinal Split Tear

The most common peroneal tendon tear. The peroneus brevis tendon splits longitudinally — creating a “C-shaped” or fully split tendon on cross-section. Often occurs after ankle sprains (the fibula creates a sharp edge that the tendon splits against) or in the presence of a peroneal groove that is too shallow. Symptoms mimic chronic ankle sprain, and the diagnosis is frequently missed until MRI is performed.

Peroneus Longus Tear

Less common than brevis tears but often associated with a painful os peroneum (sesamoid bone within the peroneus longus tendon near the cuboid). Complete tears can cause significant loss of first-ray plantarflexion and arch instability.

Peroneal Tendon Subluxation/Dislocation

Disruption of the superior peroneal retinaculum allows the peroneal tendons to snap (sublux) over the fibula. Patients report a painful “popping” or “snapping” sensation on the lateral ankle with ankle movement, particularly dorsiflexion and eversion. Often occurs with acute ankle injury or as a chronic condition in athletes.

Causes and Risk Factors

• Ankle sprains — the most common precipitating event
• High-arched (cavus) feet — place the peroneal tendons under greater strain
• Low-lying peroneus brevis muscle belly extending into the retromalleolar groove
• Retromalleolar groove that is too shallow or convex
• Chronic ankle instability — repeated ligament injuries leave the tendons vulnerable
• Excessive running mileage, especially on uneven terrain

Diagnosis

Clinical Examination

Tenderness directly over the peroneal tendons (posterior and inferior to the fibula), pain with resisted eversion and plantarflexion, and a positive “peroneal compression test” (longitudinal compression of the tendons in the groove produces pain) are highly suggestive of peroneal tendon pathology.

MRI

MRI is the gold standard for diagnosing peroneal tendon tears and tendinopathy. Axial sequences clearly show the split-tear pattern in the peroneus brevis, thickening and signal changes in tendinopathy, and superior retinaculum disruption in subluxation. Diagnostic accuracy exceeds 90% for experienced musculoskeletal radiologists.

Ultrasound

Dynamic ultrasound is excellent for detecting peroneal tendon subluxation (the tendons can be observed subluxing in real time with ankle movement) and for identifying longitudinal tears in experienced hands. More accessible and less expensive than MRI.

Treatment

Conservative (Tendinopathy, Partial Tears)

• Immobilization: Walking boot for 4–6 weeks in acute presentations
• Physical therapy: Eccentric peroneal strengthening, proprioception training, and calf flexibility
• Custom orthotics: For high-arched (cavus) feet, lateral wedging to reduce peroneal tendon stress; for hyperpronators, medial arch support
• Activity modification: Reducing running volume and avoiding surfaces that stress the lateral ankle

Surgical (Complete Tears, Subluxation, Failed Conservative Care)

• Peroneal tendon repair/debridement: Suturing of split tears with concurrent tubularization of the tendon; debridement of degenerative tissue
• Retinaculum repair/reconstruction: For peroneal subluxation — tightening or reconstructing the superior peroneal retinaculum to keep the tendons in the groove
• Groove deepening: When the fibular groove is too shallow, surgical deepening prevents recurrent subluxation
• Tenodesis or transfer: For irreparable tears, the peroneus brevis may be tenodested to the longus or vice versa

Related Conditions

• Chronic Ankle Sprain / Instability
• Custom Orthotics for Lateral Ankle Pain
• Arch & Tendon Pain

Ready to Get Relief? Book an Appointment Today.

Board-certified podiatrists Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin see patients daily at our Howell and Bloomfield Township, MI offices.

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