Chronic insertional Achilles tendinopathy secondary to congenital os Achilles: A case report

Insertional Achilles tendinopathy is a common overuse disorder affecting the foot and ankle that can lead to the development of a Haglund's deformity with chronicity, a retrocalcaneal exostosis that forms at the Achilles insertion site, further increasing pain and dysfunction. We report a case of a healthy, 35–40-year-old male with chronic left-sided insertional Achilles pain beginning in early adolescence. Physical exam demonstrated bilateral prominences on the posterior aspect of both heels, exquisitely tender on the left and without range of motion deficits. Imaging demonstrated a large calcific ossicle clearly within the tendinous insertion of the Achilles onto the left calcaneus. He underwent surgical intervention to provide pain relief and restore function. He exhibited full recovery post-operatively and has now returned to full functional activities. Given his symptom pathogenesis and progression, this patient may likely have suffered from chronic insertional Achilles tendinopathy due to an accessory ossicle that we believe was congenital. Current literature describes an additional secondary ossification center that appears over the dorsal, posterosuperior surface of the calcaneus. We suspect that there was a lapse in fusion at this additional ossification center that contributed to his pathological condition. This case report presents a unique occurrence of Achilles tendinopathy likely due to an accessory ossicle of congenital etiology. This highlights the importance of investigating the prevalence of this condition in those with chronic insertional Achilles tendinopathy, thus providing meaningful insight in considering effective treatment modalities in the management of these patients. •Insertional Achilles tendinopathy is multifactorial, but mostly an overuse disorder.•This is a unique case of a successfully treated IAT due to congenital os Achilles.•Consideration of congenital os Achilles is valuable in evaluating chronic IAT.•More studies will help guide future recognition and management for this condition.