Deep vein thrombosis (DVT) is a condition classically associated with blood stasis, hypercoagulability or injury to the vasculature. As blood stasis is usually associated with patient immobility, DVT occurrence in young active patients with no underlying haematological conditions is a rarity. An exostosis, also known as osteochondroma, is a cartilage capped lesion. If solitary, they represent low malignant potential and unless symptomatic, they are rarely excised. A 23-year-old, active male, presented to hospital with pain and swelling in the left lower leg. It was a deep, non-radiating pain, exacerbated by exercise. Wells' criteria score for DVT was 2. An ultrasound was performed which identified thrombosis in the superficial femoral, and popliteal veins. Haematological causes of thrombosis were ruled out. X-ray showed a posterior femoral exostosis. It was determined that compression by the exostosis was the cause of the thrombosis. We present a case of a DVT secondary to osteochondroma formation in a young male. Isolated DVT in this setting is uncommon with fewer than five previously reported cases identified in the literature. We also discuss the current literature and management of this rare entity.