MRCP2-0719

A 65-year-old man with a history of chronic obstructive pulmonary disease (COPD) presents to the Emergency Department after feeling a sudden snap at the base of his left ankle. He is unable to bear weight or move his foot up and down. He is currently experiencing a COPD exacerbation and was prescribed prednisolone and ofloxacin by an Emergency General Practitioner (EGP). He also takes aspirin, atorvastatin, and ramipril for hypertension and cardiovascular disease. Upon examination, a ruptured Achilles tendon is discovered. What is the most likely cause of this injury?