Peroneal Tendon Injuries

Peroneal tendon pain, tears and instability

The peroneus brevis and peroneus longus tendons pass behind the outer ankle bone (lateral malleolus). They turn the foot outward, help stabilise the ankle, and peroneus longus also supports the arch. Injuries can cause persistent pain or snapping after a sprain and may coexist with lateral ankle ligament instability or a cavovarus foot.

Main problems

Peroneal tendinopathy: load-related pain and tendon thickening.
Longitudinal split tears, especially of peroneus brevis; less often other tears or rupture.
Peroneal tendon subluxation or dislocation: the tendons shift out of the groove behind the fibula, usually following injury to the superior peroneal retinaculum.
Associated conditions: chronic ligament instability, hindfoot varus, tendon crowding or bony abnormalities.

Symptoms and examination

Symptoms may include pain and swelling behind the outside ankle bone, weakness on resisted eversion, popping or snapping with movement and difficulty on uneven surfaces. Examination distinguishes tendon pathology from ligament damage, sinus tarsi pain and other causes of lateral ankle pain. An MRI abnormality without matching clinical symptoms does not automatically need treatment.

Imaging

X-rays assess bony injury and foot alignment. MRI can show tendon splitting, degeneration and associated ligament or joint injuries. Dynamic ultrasound is particularly useful when the tendon dislocates or snaps during movement. Both ultrasound and MRI are appropriate tools; the choice depends on the clinical question and local expertise.

Treatment without surgery

Initial management is usually non-operative for tendinopathy and many symptomatic tears: adjust activity, use a brace or temporary boot when needed, gradually rebuild tendon strength and balance, and address footwear or alignment. Intratendinous steroid injection is generally avoided because of possible tendon injury. Evidence for PRP is insufficient for routine use. Shockwave therapy may be considered if symptoms persist despite rehabilitation. An acute dislocation in a non-athlete can sometimes be treated with an appropriately positioned period of immobilisation, but the tendons dislocate again in about half of cases. Surgery is usually recommended for athletes and for repeated dislocation.

When is surgery considered?

Operation is considered for persistent symptoms after a reasonable rehabilitation programme, a mechanically unstable tendon, or selected acute injuries in high-demand athletes. The aim is to treat the clinical problem, not simply to correct an MRI appearance.

Tendon debridement and repair

A repairable longitudinal tear may be debrided and sutured (tubularised) while preserving viable tendon. If a tendon cannot be repaired satisfactorily, tenodesis to the other peroneal tendon, graft reconstruction or another reconstructive option may be considered.

Stabilisation of a dislocating tendon

The superior peroneal retinaculum can be repaired or reconstructed. Fibular groove deepening is commonly added for long-standing (recurrent) dislocation and in athletes; in other cases it depends on the groove anatomy. Procedures should also address relevant coexisting lateral ligament instability or cavovarus alignment where appropriate.

Recovery and risks

After tendon repair or stabilisation, protection in a boot or cast is followed by staged movement, strengthening and balance rehabilitation. When the retinaculum has been repaired, the ankle is usually protected in a boot or cast for about 6 weeks before the tendons are loaded; return to sport commonly takes 3–6 months. Most people can drive again at about 6–8 weeks. Risks include wound problems, infection, sural nerve irritation, stiffness, tendon scarring, persistent pain, repair failure or recurrent dislocation. Contact the rooms promptly if you develop a fever, increasing wound redness or discharge, severe worsening pain or calf swelling after surgery; call 111 for chest pain or breathlessness.

Common questions

Is snapping outside the ankle always a peroneal tendon dislocation?
No. A clinical assessment and sometimes dynamic ultrasound help identify the source.

Does every MRI-reported split tear require surgery?
No. Symptoms, function and the examination are essential to treatment choice.

Can tendon tears occur with ankle ligament injuries?
Yes, and both may need evaluation.

Will groove deepening always be performed?
No. It depends on the injury, anatomy and reconstruction plan.

Seeking specialist advice

Persistent posterolateral ankle pain, weakness or reproducible snapping deserves assessment, particularly when symptoms persist after an apparent ankle sprain. If your symptoms followed an injury, ACC may cover part of the cost; see the ACC questions on our Your appointment page.

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