Case Report

Hypertrophy of the Peroneal Tubercle: A Rare Cause of Peroneal Tendon Synovitis

by Quentin Vermeulen1*, Tina Decorte1, Annick Viaene1, Brecht De Coninck2, Karel Watteyne2, Luc Vanden Bossche1

1Department of Physical and Rehabilitation Medicine, Ghent University Hospital, Ghent, Belgium

2Department of Physical and Rehabilitation Medicine, AZ Sint-Jan, Bruges, Belgium

*Corresponding author: Quentin Vermeulen, Department of Physical and Rehabilitation Medicine, Ghent University Hospital, Ghent, Belgium

Received Date: 25 August 2023

Accepted Date: 29 August 2023

Published Date: 31 August 2023

Citation: Vermeulen Q, Decorte T, Viaene A, De Coninck B, Watteyne K, et al (2023) Hypertrophy of the Peroneal Tubercle: A Rare Cause of Peroneal Tendon Synovitis. Ann Case Report. 8: 1428. DOI:10.29011/2574-7754.101428


Hypertrophy of the peroneal tubercle is a rare cause of peroneal tendon synovitis. The peroneal tubercle of the calcaneal bone is an anatomical structure that has both structural and biomechanical functions. When abnormal in shape and size, it can cause friction or impingement of the peroneal tendons, resulting in tenosynovitis and/or tendon tears. Clinically, the patient presents with tenosynovitis and a prominent peroneal tubercle palpable on the lateral calcaneus. Radiographs and ultrasound are sufficient for diagnosis. Additional CT and MRI are often performed to better visualize the bony structures and soft tissues, respectively. Treatment consists of conservative therapy for at least 6 weeks. If conservative therapy fails, or if the tendon is torn, surgery may be required.


We describe the case of a 65-year-old woman with peroneal tendon synovitis due to hypertrophy of the peroneal tubercle. The peroneal tubercle is a well-known anatomical structure on the lateral calcaneus. Abnormalities in its shape and/or size can result in tenosynovitis of the peroneal tendons. In this article, we discuss the anatomy and function of the peroneal tubercle. Next, we will highlight the pathogenesis of tubercle hypertrophy and how it can lead to peroneal tendon tenosynovitis. Finally, diagnosis and treatment management are discussed.

Case presentation

A 65-year-old woman with a relevant history of diabetes and diabetic polyneuropathy presented with spontaneous pain and swelling of the right lateral ankle. The pain was present on exertion, with significant pain at night. Clinical examination revealed an ataxic gait, part of the known polyneuropathy. The gait was antalgic on the right side. On inspection, we noted significant pedes cavovari and transversi, more pronounced on the right than the left side (Figure 1). There was visible swelling and pain on palpation of the distal fibula and lateral calcaneus. A bony mass was palpable in the mid lateral third of the calcaneus. Pain was provoked by passive ankle inversion and resisted eversion.

Figure 1: Pedes cavovari with lateral deviation of the subtalar joint axis, metatarsus adductus, hallux valgus and pes transversus. Varus deformity of the calcaneus induces traction on the lateral calcaneus and peroneal tendons.

Based on the clinical findings, tenosynovitis of the peroneus longus and/or brevis was suspected. Ultrasound showed enlarged tendon structures, synovial hyperproliferation and increased fluid in the tendon sheaths of the peroneus longus and brevis muscles with hypervascularisation and peritendinous subcutaneous oedema. These findings supported our clinical diagnosis. We also noted a prominent bony structure at the lateral calcaneus, in close contact with the peroneus longus and brevis tendons. Dynamic evaluation, obtained during ankle inversion and eversion movements, showed reduced tendon gliding over this bony structure (Figure 2).