Two bony projections or protuberances may be seen from the lateral wall of the calcaneum – the peroneal tubercle and the retrotrochlear eminence.
The peroneal tubercle is present immediately inferior to the fibular malleolus, lying in between the two tendons, it separates the tendons of peroneus brevis and the peroneus longus. The common synovial sheath that covers the two tendons proximal to the tubercle, divides into two slips to individually enclose the peroneal tendons at the tubercle and beyond. The peroneus brevis lies superior to the tubercle and the peroneus longus lies inferior to the tubercle.
The retrotrochlear eminence is located posterior to the peroneal tubercle and the peroneal tendons. It is seen to be prominent in individuals with hypertrophied peroneus quartus muscle, the most frequently reported assessor y peroneal muscle. The muscle arises from the inferolateral aspect of the fibula and has variable insertions, one of them being the retrotrochlear eminence.
The peroneal tubercle, also called the peroneal trochlea, may enlarge – when it is called Hypertrophied tubercle. The enlarged tubercle may impinge upon the peroneus tendons and result in stenosing tenosynovitis. The axial radiograph ,CT scan and MRI of the calcaneum show the hypertrophied tubercle. The tendon sheaths show thickening and fluid within them.
At times an adventitial bursa can develop over the tubercle due to repeated friction , which may become symptomatic.
The initial management of the condition when symptomatic is conservative, but surgical resection is indicated in those who do not respond to conservative management.