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Health condition · Clinically reviewed

Peroneal tendinopathy, lateral ankle tendon disease — from bracing to endoscopic peroneal tendoscopy.

The peroneal tendons run behind the outer ankle bone. They can become painful, tear, or slip out of their groove. Most cases settle with bracing, eccentric loading and shockwave. When they don’t, keyhole tendoscopy or open repair usually does.

Jump to treatment See red-flag lateral ankle pain
A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Clinically reviewed

    Our editorial team writes each guide. A registered UK clinician then reviews it before we publish.

  • 02

    Sourced from guidance

    We check every claim against BOFAS, AOFAS or peer-reviewed sources. You can see them at the end.

  • 03

    Current for 2026

    This guide reflects current UK and international guidance. It covers bracing, loading, shockwave and endoscopic tendoscopy.

Key facts

Peroneal tendinopathy at a glance.

The essentials in plain English. What peroneal tendon disease is, why outer ankle pain and slipping happen, and what the evidence says actually helps.

  • Definition

    Peroneal tendinopathy is a range of problems affecting the tendons behind the outer ankle bone. These range from a painful tendon, to a long tear along the fibres, to a tendon that slips out of its groove.

  • Associations

    It is often linked to a cavus (high-arched) foot posture. It also happens with chronic ankle instability after repeated outer ankle sprains.

  • Investigation of choice

    MRI combined with dynamic ultrasound is the best test. Ultrasound picks up a tendon that slips (subluxation) — something a still MRI can miss.

  • Retinaculum injury

    The superior peroneal retinaculum is a band that holds the tendons in place. Injury to it lets the tendons slip over the fibula.

  • Minimally invasive

    Endoscopic peroneal tendoscopy is the modern keyhole option. It can both diagnose and treat the problem in one sitting.

  • Recurrent subluxation

    For tendons that keep slipping, surgeons deepen the fibular groove and rebuild the retinaculum. This is the definitive fix.

Why this guide matters

Bracing and loading first, tendoscopy when needed.

Peroneal tendon disease is often missed. This guide sets out the step-by-step pathway from bracing to endoscopic tendoscopy, so nothing is overlooked.

  • Bracing and loading come first

    A heel wedge, an ankle brace and slow, steady loading settle most peroneal tendinopathy without surgery.

  • Dynamic ultrasound catches subluxation

    A still MRI can miss tendons that slip only during movement. Dynamic ultrasound is the key test to spot a slipping tendon.

  • Tendoscopy is the modern minimally invasive option

    Endoscopic peroneal tendoscopy repairs the tendon and clears inflamed tissue. It causes less soft-tissue damage than open surgery.

How the diagnosis is made

From lateral ankle pain to a clear plan.

The steps a UK GP or foot and ankle team will usually follow, in order. This way you know what to expect, and why.

  1. 01

    Recognising

    Symptom + sprain history

    Pain on the outer ankle is the main clue. Many patients have had repeated sprains, or feel the tendon slip over the fibula.

  2. 02

    Recognising

    Palpation posterior to lateral malleolus

    The doctor presses just behind the fibula, along the tendon sheath. Tenderness here is the single most useful sign.

  3. 03

    Recognising

    Provocative tests

    A single-leg heel raise turned outwards, resisted eversion and circling the ankle can bring on the pain or a snap.

  4. 04

    Confirming

    Dynamic ultrasound

    A live ultrasound scan taken while you move the ankle outwards can catch the tendon slipping. This is the key finding.

  5. 05

    Confirming

    MRI of the ankle

    MRI shows tendon splits, inflammation of the tendon sheath (tenosynovitis) and any injury to the retinaculum or nearby bone.

  6. 06

    Confirming

    Assess foot alignment

    A cavus (high-arched) foot puts extra strain on the peroneals. Spotting this changes how we treat the problem.

  7. 07

    Managing

    Foot & ankle surgery consultation

    A specialist reviews cases that do not settle, confirmed tears, or a tendon that keeps slipping. Options include tendoscopy, repair and groove-deepening.

Typical timeline: 3–6 weeks from first appointment to a settled plan.

Symptoms

What peroneal tendinopathy actually feels like.

The pattern is telling. Pain sits on the outer ankle behind the fibula, sometimes with a click or snap. It often follows a run of ankle sprains.

  • Lateral ankle pain

    Pain along the outside of the ankle. The peroneal tendons sit behind the fibula.

  • Pain behind fibula

    A sore spot just behind the outer ankle bone, along the tendon sheath.

  • Clicking / snapping

    A click or snap over the fibula when you move the ankle. This often means the tendon is slipping.

  • Local swelling

    Swelling behind the fibula. It may feel warm if the tendon sheath is inflamed.

  • Peroneal subluxation on movement

    The tendon jumps forward over the fibula when you turn the foot outwards. You can often bring this on to order.

  • Weakness in eversion

    Less power when turning the foot outwards against resistance. This can point to significant tendon damage or a tear.

  • Recurrent symptoms

    Repeated ankle sprains, a feeling of the ankle giving way, and pain that never fully settles between episodes.

  • Red flag

    A sudden traumatic tendon dislocation with the ankle locking. This needs urgent foot and ankle surgical review.

Treatment

How peroneal tendinopathy is treated in the UK.

A step-by-step approach. Bracing and loading come first. Shockwave and ultrasound-guided injections come next. Endoscopic tendoscopy and groove-deepening are kept for cases that don’t settle or where the tendon keeps slipping.

  • Lateral heel wedge / brace

    A wedge on the outer heel, or an ankle brace, takes strain off the tendons. It also supports a high-arched or unstable hindfoot.

  • Physiotherapy (eccentric loading)

    Slow, controlled loading of the tendons (eccentric loading) is the proven core of non-surgical rehab.

  • Ankle stabilising exercises

    Balance training and targeted peroneal strengthening cuts the cycle of sprain, slipping and tear.

  • Shockwave therapy (ESWT)

    Extracorporeal shockwave therapy (ESWT) can help when loading alone has not settled the tendon.

  • NSAIDs

    A short course of anti-inflammatory tablets (NSAIDs) can ease an inflamed tendon sheath. They control symptoms rather than cure the problem.

  • Ultrasound-guided injection

    An ultrasound-guided injection places steroid around the tendon sheath. It is never given into the tendon itself, as this risks rupture.

  • Endoscopic peroneal tendoscopy + repair

    Keyhole tendoscopy lets surgeons clear out inflamed tissue and repair long splits in the tendon. Recovery is quicker than open surgery.

  • Groove-deepening + SPR reconstruction

    Surgeons deepen the fibular groove and rebuild the superior peroneal retinaculum. This is the definitive fix for a tendon that keeps slipping.

What this guide is based on

The sources behind every claim on this page.

UK and international foot and ankle society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, physiotherapist or foot and ankle team knows your history. They can tell you which parts apply to you. If in doubt, get seen.

  • British Orthopaedic Foot and Ankle Society (BOFAS). Peroneal tendon disorders — patient information and clinical standards.

  • NICE. Musculoskeletal guidance on tendinopathy assessment and management.

  • American Orthopaedic Foot & Ankle Society (AOFAS). Peroneal tendon injuries — clinical guidance.

  • Sports Medicine Australia. Tendinopathy management guidance.

Red flags

When lateral ankle pain is more than tendinopathy.

Most peroneal pain settles with bracing and loading. These are the situations where you should think about a different diagnosis or a surgical opinion.

  • Acute peroneus brevis tear

    A sudden, sharp pain on the outer ankle with weakness turning the foot outwards, after rolling the ankle. It needs prompt imaging and a surgical opinion.

  • Peroneal tendon dislocation

    A traumatic slip of the tendons over the fibula, with the ankle locking or unable to move. This needs urgent surgical review.

  • Post-op nerve injury (sural)

    New numbness or burning on the outer foot after tendon surgery. This may mean the sural nerve is injured — contact your team.

  • Failed conservative therapy

    Pain, weakness or clicking that carries on after 3 to 6 months of bracing, loading and shockwave. It is time for a surgical opinion.

  • Chronic ankle instability with tear

    Repeated sprains together with a confirmed tendon tear. Physio alone is not enough — this needs combined ligament and tendon surgery.

  • Cavus foot deformity

    A high-arched foot that turns inwards puts too much load on the peroneals. Realignment surgery may be needed along with tendon repair.

  • Post-op wound complication

    Growing redness, discharge, swelling or fever after tendoscopy or open repair. Get a same-day surgical review.

  • Recurrent subluxation

    The tendon keeps snapping over the fibula despite bracing. The definitive treatment is groove-deepening and rebuilding the retinaculum.

  • Peroneus quartus variant

    Some people have an extra muscle called the peroneus quartus. It can crowd the tendon groove and add to the problem — MRI picks it up.

Living with it

A slow tendon, but a very manageable one.

Four things make the biggest day-to-day difference: loading, bracing, load management and patient review.

A quiet reminder

Consistency beats intensity, every time.

Small, steady changes kept up for months do more than a heroic week that doesn’t last.

  1. 01 Rehab

    Load the peroneals, patiently

    Slow, steady loading over months is dull and unglamorous. It is also the single biggest lever for non-surgical care.

  2. 02 Bracing

    Support a cavus or unstable ankle

    A heel wedge or ankle brace cuts the risk of another sprain. It also takes strain off the tendons during high-risk activity.

  3. 03 Load

    Modify, do not stop

    Cut back on cutting sports and uneven-ground running while you heal. Do not stop moving altogether.

  4. 04 Reviews

    Reassess in months, not weeks

    Book a review at 3 and 6 months. If symptoms persist despite good rehab, move up to shockwave or a surgical opinion.

Frequently asked

Everything we get asked about peroneal tendinopathy.

Quick answers on bracing, loading, shockwave, tendoscopy and when to seek help.

  • What actually is peroneal tendinopathy?

    It is a range of problems affecting the peroneus longus and brevis tendons behind the outer ankle bone. These range from an inflamed tendon sheath, to long splits in the tendon, to a tendon that slips fully over the fibula.

  • What causes peroneal subluxation?

    The superior peroneal retinaculum is a band that holds the tendons in their groove. When it is injured — usually after an ankle sprain with the foot pulled upwards — the tendons can slip forward. Many patients feel this as a click or snap.

  • Do I need an MRI?

    MRI is the best test for tendon splits and inflammation of the tendon sheath. A dynamic ultrasound is usually needed too, to catch a tendon that slips only during movement. A still MRI can miss this.

  • What is endoscopic peroneal tendoscopy?

    It is a keyhole procedure through two small cuts along the tendon sheath. The surgeon can look inside, clear out inflamed tissue and repair long splits. It causes less soft-tissue damage than open surgery.

  • What is groove-deepening surgery?

    The surgeon deepens the groove in the fibula and rebuilds the retinaculum. This holds the tendons in place. It is the definitive treatment when the tendons keep slipping.

  • When should injections be avoided?

    Steroid must never be injected into the tendon itself — the risk of rupture is real. When an injection is used, it is placed around the tendon (in the sheath) under ultrasound guidance.

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