- The peroneal tendons run behind the outside ankle bone and stabilize the foot during push-off.
- They become inflamed from overuse — particularly in runners, hikers, and people with high-arched feet.
- Pain is on the outside and back of the ankle, worse with activity, and often described as a chronic ache.
- Most cases respond to rest, physical therapy, bracing, and custom orthotics.
- Chronic or torn tendons sometimes need surgical repair.
What is peroneal tendonitis?
The peroneal tendons are two tendons (peroneus longus and peroneus brevis) that run from the lateral side of the lower leg, behind the outside ankle bone, and attach to bones on the outside of the foot. Their job is to stabilize the foot during push-off and to prevent the ankle from rolling inward. When they're overused or injured, they become inflamed or can develop longitudinal splits or tears.
Peroneal tendonitis is most common in runners (especially those with high-arched feet who overload the lateral foot), hikers, dancers, and athletes in sports that require quick lateral movements. It can also develop after an ankle sprain. Chronic ankle instability and peroneal tendonitis often coexist.
At NES, we treat peroneal tendonitis with a stepped plan: relative rest, physical therapy emphasizing peroneal strength and balance, custom orthotics to correct mechanical overload, and bracing for severe cases.
See it in motion
Animations licensed from ViewMedica · Swarm Interactive
What it feels like
Peroneal tendonitis has a recognizable location and pattern:
- Pain on the outside and back of the ankle, behind the lateral ankle bone
- Pain that worsens with activity and improves with rest
- Tenderness when you press directly on the tendons
- Swelling along the tendon path
- Pain reproduced by resisted eversion (turning the foot outward against resistance)
- A snapping or popping sensation in some cases
- Weakness pushing off the outside of the foot
Why it develops
Peroneal tendonitis develops from mechanical overload:
- High running mileage, particularly on uneven surfaces
- High-arched (cavus) foot structure that overloads the outside of the foot
- Previous ankle sprain — the same injury that stretches the lateral ligaments
- Worn or unsupportive footwear
- Tight calf muscles increasing tendon strain
- Chronic ankle instability creating repeat micro-injury
How we diagnose peroneal tendonitis
Diagnosis is clinical — the location of pain, the reproduction of pain with resisted eversion, and the absence of a typical sprain mechanism point to peroneal tendonitis. MRI is useful for confirming inflammation versus a longitudinal split or tear, and for surgical planning.
Non-surgical care
Conservative care resolves most cases:
- Relative rest from the offending activity
- Physical therapy with peroneal strengthening, calf flexibility, and balance work
- Custom orthotics with a lateral heel post and arch support to unload the tendons
- Anti-inflammatory medication during flares
- A walking boot for severe cases (1–3 weeks)
- Eccentric strengthening as the tendon recovers
- Gradual return to running with mileage progression
Surgical care
Surgery is considered for chronic tendonitis that hasn't responded to conservative care, for confirmed tendon splits or tears, and for peroneal subluxation.
- Tendon debridement and repair of longitudinal splits
- Tubularization of the brevis tendon for chronic split tears
- Tendon transfer for irreparable tears
- Peroneal retinaculum reconstruction for chronic subluxation
- Calcaneal osteotomy when high arch is driving the tendonitis
Post-surgical recovery typically involves 2 weeks of non-weight-bearing in a splint, transition to a walking boot for 4–6 weeks, then physical therapy and gradual return to activity. Return to running and full sport is usually 3–4 months.
When to see a specialist
- Outside-of-ankle pain that has lasted more than 3 weeks
- Ankle pain that's worse with activity and not improving
- A snapping or popping sensation behind the outside ankle bone
- A history of chronic ankle sprains plus new outside-ankle pain
Peroneal tendonitis is treated by Dr. Todd Galle and Dr. Manny Moy (sports medicine focus), with surgical repair by Dr. Yama Dehqanzada or Dr. Thomas Melillo when needed.