Fibular retinacula

Peroneal retinacula
The mucous sheaths of the tendons around the ankle. Lateral aspect. (Peroneal retinacula not labeled, but region visible at bottom left.)
Details
Latin	Retinaculum musculorum peronaeorum
Anatomical terminology []

The peroneal retinacula (singular: peroneal retinaculum) are fibrous retaining bands which bind down the tendons of the peroneus longus and brevis as they run across the side of the ankle. (Retinaculum is Latin for retainer).

These bands consist of superior and inferior fibres. The superior fibres are attached above to the lateral malleolus and below to the lateral surface of the calcaneus. The inferior fibres are continuous in front with those of the inferior extensor retinaculum of the foot; behind they are attached to the lateral surface of the calcaneus; some of the fibers are fixed to the calcaneal tubercle, forming a septum between the tendons of the peroneus longus and peroneus brevis muscles.

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)