The short answer
Peroneal tendinopathy is irritation, degeneration, or partial tearing of the two peroneal tendons that run behind the outer ankle bone, causing pain and swelling along the outer ankle and sometimes a snapping sensation. It often follows ankle sprains or occurs with ankle instability, and usually improves with bracing, physical therapy, and ultrasound-guided PRP or tendon scraping for stubborn cases.
Medically reviewed by Marc Gruner, DO, MBA, RMSK
Sports medicine physician, Mayo Clinic fellowship. Last reviewed June 2026
Overview
The peroneal tendons stabilize the outer ankle and help turn the foot outward. Repetitive load, ankle instability, or a prior sprain can irritate, degenerate, or partially tear them, producing pain and swelling behind the outer ankle bone that worsens with activity and uneven ground — and occasionally a snapping feeling as a tendon shifts.
Dr. Gruner uses ultrasound to characterize the tendons and any instability, then builds a program of bracing, peroneal and balance strengthening, and activity modification. For chronic, degenerative cases, ultrasound-guided PRP or tendon scraping can support healing, with surgery reserved for significant tears or dislocating tendons.
Common symptoms
- Pain and swelling along the outer ankle
- Pain worse on uneven ground
- A snapping sensation behind the ankle bone
- A sense of ankle instability
What to expect at your visit
- 1.
A focused conversation
Dr. Gruner reviews your history, prior imaging, and goals — what you want to get back to doing.
- 2.
Point-of-care ultrasound
When useful, a diagnostic musculoskeletal ultrasound evaluates the injury in real time, with no radiation.
- 3.
A clear, individualized plan
You leave understanding the diagnosis, the non-surgical options, and the expected timeline — in plain language.
Frequently asked questions
- Why does the outside of my ankle still hurt after a sprain?
- Lingering outer-ankle pain after a sprain is often peroneal tendinopathy or instability rather than the original ligament. Ultrasound clarifies the cause, and a program of bracing, targeted strengthening, and — for chronic cases — PRP or tendon scraping usually resolves it.