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Peroneal subluxation

The tendons on the outside of the ankle slip in and out of their correct location, making the ankle feel unstable. The tendons are also more likely to tear or rupture if they have slipped out of place.

What is it?

The tendons are elastic strips of tissue that connect muscle to bone. In the ankle joint, the two peroneal tendons run side by side behind the outer ankle bone. One of the tendons attaches to the outer part of the midfoot, and the other runs under the foot and attaches near the arch. The tendons pass through a groove in back of the fibula (calf bone), which is covered by a ligament called retinaculum. This ligament is designed to keep the tendons in place.

If there has been a sprain or similar injury, the retinaculum can break and peroneal tendons can slip out of their groove. This causes the tendon to be stretched, and results in instability. The tendons are also more likely to tear or rupture if they have slipped out of place.

How does it feel?

You might feel occasional pain behind your anklebone. You might also feel a snapping feeling as the tendon slips in and out of its position behind the ankle bone. You will almost certainly feel an instability or weakness in your ankle. There is also likely to be some swelling around the outside of the ankle.


The surgeon will examine the foot and look for pain, instability, swelling, warmth and weakness on the outer side of the ankle. An MRI scan or ultrasound may be needed to fully evaluate the injury.


Using minimally invasive surgery, the surgeon can deepen the groove in the back of the fibula, so that the tendons are more likely to stay in position. The surgeon will then repair the torn retinaculum ligament, which will hold the peroneal tendon in place.


You will usually have to spend four to six weeks in an aircast boot, and then a short physiotherapy programme. Full recovery should be expected after three months.

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