Peroneal tubercle hypertrophy

Case contributed by Maulik S Patel


Focal swelling involving both hind feet on the lateral aspect since birth. Recent onset of mild local pain.

Patient Data

Age: 5 years
Gender: Female

There is a bump inferior to the lateral malleolus in both feet. It is more obvious on right than the left side. It is associated with overlying skin pigmentation.


There is a well-defined triangular shaped hypoechoic area between peroneus longus and brevis tendons in the inframalleolar region.  Peroneal tendons show normal echopattern without tenosynovitis. Findings are present on both sides.

Annotated image

The unossified peroneal tubercle is outlined.

Case Discussion

A girl presented with swelling and mild pain on the inframalleolar region of both feet on the lateral aspect. Ultrasound of both feet shows a hypoechoic triangular shaped area separating peroneus longus and peroneus brevis tendons. This hypoechoic area is non-ossified hypertrophic peroneal tubercle. It shows about 4.5 mm in height from calcaneum. There is no associated peroneal tendon pathology or overlying bursitis. 

The peroneal tubercle is an anatomical structure from the lateral aspect of the calcaneum. The inferior peroneal retinaculum is attached to it. Tubercle can be absent, hypoplastic or large in size. It may show abnormal contour also.

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