This article discusses the most common diagnostic dilemmas when trying to distinguish between tumor and sports injury or other trauma. Bone tumors frequently occur in the same young active patients who experience sports injuries. If the pain persists longer than expected, imaging studies should be obtained to prevent a delay in diagnosis or an inappropriate arthroscopy. A history of spontaneous fracture or a fracture after minor trauma should raise suspicion for underlying lesion as the cause. Occasionally necrosis and/or hemorrhage within a soft tissue sarcoma is so extensive that only a small cuff of viable tumor tissue is present.