An OIH is a poorly understood pathology. Although benign, these lesions can cause significant morbidity, and surgical excision is a reasonable and safe treatment option. OIHs may be distinguished from related calcified intramuscular pathologies based on key clinical features and distinct histopathology. Clinically, they are characterized by a history of remote trauma and, on histopathology, by compact, mature bone in the setting of an old, organizing hematoma. Despite this, similarities with other calcified intramuscular pathologies persist, and further study is warranted to better understand and classify these lesions.