Leg swelling in patients with paraplegia due to spinal cord injury (SCI) occurs for various reasons, including heterotopic ossification (HO), deep vein thrombosis (DVT), fracture, or cellulitis. The clinical presentations of these conditions may overlap in part or in whole and it may occasionally be difficult to distinguish. Of these conditions, DVT and subsequent pulmonary embolism remain significant causes of morbidity and mortality in patients with SCI. Therefore, a prompt diagnostic work-up, particularly for DVT, is essential in patients with SCI, who present with leg swelling. Here, we report a case of leg swelling in a paraplegic patient, resulting from HO mimicking DVT and discuss the differential diagnosis.