In brief: Groin strains (and injuries assumed to be groin strains) have been treated with a simple, straightforward approach. However, complications too often arise from inadequate diagnosis or improper management of these injuries. A pelvic stress fracture, an avulsion injury, and even a tumor can be confused with a groin strain. This article discusses the importance of differential diagnosis, which can help prevent serious complications. The authors also present a case report of a football player who was diagnosed with myositis following a groin strain he had sustained a year earlier.