Painful conditions of the musculoskeletal system are encountered quite frequently and are generally benign. However, clinicians should be careful to exclude rare malignant disorders and soft tissue sarcomas such as rhabdomyosarcoma, which have no specific symptoms or findings. This paper presents a case that was initially consistent with a hematoma but was then diagnosed as a rhabdomyosarcoma upon clinical examination and ultrasonography at follow-up shortly after.