The peroneal tendons (peroneus longus and peroneus brevis), also called the fibular tendons, are a pair of tendons that run from the calf down into the foot just behind the fibula (lateral malleolus or outer bone of the ankle).  They can develop a number of problems.

Peroneal Tendinopathy

Also called Peroneal tendonitis, tendonosis or tenosynovitis, this is a condition in which the tendons become thickened and degenerate. They may develop splits or partial tears within them. There may also be inflammation of the peroneal tendon sheath.


Peroneal tendinopathy is occasionally caused by an isolated injury, or inflammatory conditions such as Rheumatoid arthritis, but is more usually the result of an over-use injury in someone aged over forty. Being diabetic or overweight, and having a high arched foot or tight calf muscles, may also play a role.


Pain is felt on the posterolateral corner of the ankle (outer side just behind the fibula bone). It is usually made worse by activities such as running or jumping. There may be swelling and tenderness of the area and sometimes a nodule may be felt on the tendon.


Your doctor may be able to diagnose peroneal tendinopathy from your symptoms and by examining your ankle but MRI or ultrasound scans can add valuable information about the state of the tendons.


Peroneal tendinopathy often responds to conservative measures such as physiotherapy, exercises, orthotics (insoles) or a period of rest in a walker boot.

If such measures are ineffective surgery to remove the inflamed or damaged tissue and repair any splits or tears in the tendons may be needed.

Peroneal Tendon Subluxation

In this relatively uncommon condition the peroneal (fibular) tendons that normally run in a shallow groove on the back of the fibula (outer ankle bone) sublux or dislocate out of their groove and can slip forwards around the side of the ankle.

It is usually caused by an injury in which the roof of the groove (retinaculum), which holds the tendons down, is torn. It is more common in people who have a shallower fibular groove.

It is often mistaken for and ankle sprain and can cause weakness and instability of the ankle.

Your doctor may be able to make the diagnosis from your symptoms and by examining your ankle, especially if you can demonstrate the tendons subluxing or dislocating. If there is doubt ultrasound or MRI scans may be useful.

Peroneal tendon subluxation can respond to conservative measures such as rest in a walker boot or plaster cast and physiotherapy, especially if the injury is fresh. Otherwise surgery to repair the retinaculum, often combined with deepening the fibular groove, may be needed.