Peroneal Tendinopathy: The Outer Ankle Pain That's Often Missed

What are the peroneal tendons?

The peroneus longus and brevis muscles run along the outside of the lower leg and wrap behind the lateral malleolus (the outer ankle bone). They evert the foot (turn it outward) and are critical for lateral ankle stability.

When these tendons are overloaded, they become painful, sometimes swollen, and occasionally develop longitudinal tears. The pain is felt behind or below the outer ankle bone, typically worsening with running and improving with rest - a hallmark of tendinopathy.

Why runners get it

• Ankle sprains - a prior sprain can alter the mechanics and load distribution on the peroneals
• Trail running and uneven surfaces - constant lateral corrections demand repeated peroneal activation
• Sudden mileage increases
• High-arched or supinating foot - places more load on the lateral foot structures
• Worn-out shoes - loss of lateral support

Distinguishing from other lateral ankle injuries

Peroneal tendinopathy is located just behind the fibula and along the tendon course. An ankle sprain typically involves the ligaments, which are slightly different in location. A snapping peroneal tendon involves the tendon subluxing around the fibula, which is a different diagnosis.

The exercises

1. Isometric eversion

Push the outside of the foot against the wall with the ankle in neutral. Hold 30–45 seconds, 4 sets. Manages pain without provoking the tendon.

2. Resisted eversion with band

Band around the forefoot, sitting with leg straight. Turn foot outward against resistance, hold 2 seconds, return slowly. 3 sets of 15.

3. Single-leg calf raise with eversion

Rise up on one leg, slightly emphasising the outer edge of the foot at the top. 3 sets of 15. Loads the tendons in a functional position.

4. Lateral ankle balance

Single-leg balance on a slightly unstable surface. 3 × 45 seconds. Trains the real-time activation that protects the peroneals during running.

5. Side-stepping with band

Loop a band above the ankles, step laterally with resistance. 3 × 20 steps each direction. Trains the peroneals in a sport-specific pattern.

Footwear considerations

A shoe with adequate lateral support helps during recovery. If you supinate, a more neutral shoe with a firm midsole is better than a highly cushioned one that collapses laterally.

Return to trail running

Wait until you're symptom-free on flat road running before returning to trails. The unpredictability of trail surfaces demands fully functioning peroneal tendons. Start with gentle trails before technical terrain.

Timeline

6–8 weeks for most cases. Peroneal tendinopathy involving a longitudinal split or subluxation may require longer rehabilitation or, rarely, surgical consultation.