Cystic degeneration and calcification of the leg are uncommon late sequelae of compartment syndrome. Previously reported cases have all involved the anterior compartment of the leg. We present a 68-year-old man with a mass in the superficial posterior compartment of the leg who presented 37 years after the initial trauma and ischemic myonecrosis. MRI was useful in establishing the diagnosis and early surgical intervention. The mass was excised and closed primarily over a drain. Patient was followed up for 29 months, and there were no secondary infections, chronic sinus formation, or recurrences. Based on our experience and the available literature review, we recommend considering either excision and primary closure, or repeated needle aspiration of the mass. Packing the wound and delayed closure may lead to secondary infection, chronic sinus formation, and lower limb amputation as potential complications.