Peroneal tendonitis is inflammation of the peroneal tendons — the two tendons (peroneus longus and peroneus brevis) that run along the outside of the ankle and down the outer edge of the foot. These tendons are responsible for everting the foot (rolling it outward) and stabilizing the ankle during walking, running, and lateral movements.

What Causes Peroneal Tendonitis?

Peroneal tendonitis is most commonly an overuse injury, but it can also result from acute injury. Primary causes include:

• Repetitive ankle inversion — running on uneven surfaces, trails, or banked roads puts chronic stress on the peroneal tendons
• Ankle sprains — a lateral ankle sprain can directly injure the peroneal tendons; peroneal tendon injuries are often misdiagnosed as “ankle sprains” when the tendon is the true pathology
• High-arched (cavus) foot — increases the mechanical load on the peroneal tendons due to greater forefoot supination
• Sudden increase in training volume — marathon training, new sport participation, or return to activity after a break
• Poorly fitting footwear — shoes lacking lateral stability or with excessive heel drop

Symptoms of Peroneal Tendonitis

• Pain along the outer edge of the ankle and foot, often described as aching or burning
• Swelling and warmth along the course of the peroneal tendons (behind and below the lateral ankle bone)
• Pain that worsens with activity and improves with rest
• Tenderness to touch along the tendon path
• Occasional snapping or popping sensation at the ankle (subluxing peroneal tendons)
• Ankle instability or weakness with side-to-side movements

Peroneal Tendonitis vs. Ankle Sprain: Key Differences

Both conditions cause outer ankle pain. Peroneal tendonitis pain is typically located along the tendon course (2–4 cm behind and below the lateral malleolus), whereas a classic ankle sprain (anterior talofibular ligament) causes pain at the front of the lateral ankle. Peroneal tendonitis also tends to produce pain with resisted eversion (turning the foot outward against resistance), which is a key clinical test. Ultrasound or MRI provides definitive diagnosis.

Treatment for Peroneal Tendonitis

Conservative Treatment (8–12 weeks)

• Relative rest — reduce or eliminate the aggravating activity; cross-train with swimming or cycling to maintain fitness
• Ice and anti-inflammatory medication — for acute flares (10–15 minutes ice massage 2–3 times daily)
• Physical therapy — eccentric strengthening of the peroneal muscles, proprioception training, and ankle stability exercises are the cornerstone of recovery
• Custom orthotics — lateral wedging can reduce the mechanical strain on the peroneal tendons; particularly important for cavus foot types
• Ankle bracing — an lace-up brace reduces inversion stress during recovery and return to sport

Advanced Treatment

• PRP injection — platelet-rich plasma accelerates tendon healing in cases that have not responded to conservative care
• Ultrasound-guided corticosteroid injection — reduces acute inflammation; used sparingly due to risk of tendon weakening
• Shockwave therapy (ESWT) — effective for chronic peroneal tendinopathy with degenerative changes
• Surgery — indicated for peroneal tendon tears, chronic subluxation, or cases refractory to 3+ months of conservative treatment

Return to Sport Timeline

Most runners and athletes with peroneal tendonitis return to full activity within 6–12 weeks with proper treatment. The key is addressing the biomechanical cause (foot type, training errors, footwear) — not just treating the symptoms. Without correction of the underlying mechanics, recurrence is common.

Dr. Tom Biernacki, DPM

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.