We report the case of a 66-year-old male patient with massive ossification of the distal portion of the Achilles tendon, as a late consequence of a surgical release for club foot conducted in his childhood. The singularity of the case report derives from its clinical features: the bone mass was of abnormal dimensions, almost substituting the entire tendon; the condition had always been asymptomatic, without deficits in range of motion, in absence of either pain or biomechanical defects with age. In fact, the condition was diagnosed just recently as a consequence of a tear. Despite an ultrasound diagnosis after the injury, only during the surgical treatment, a proper evaluation of the entity of the pathology was possible. Although the ossification of Achilles tendon is a rare clinical condition with a complex multifactorial etiology, in our case report, some of the elements in the patient's medical history could be useful for the pathogenesis and early diagnosis of the disease. The aim of this case report is to emphasize the importance both of a correct evaluation of clinical history and of an accurate diagnosis, in order to conduct a proper management of this pathology.