An Unusual Presentation of Myositis Ossificans in a Pediatric Patient.

BACKGROUND: Myositis ossificans (MO) is a rare, non-neoplastic lesion characterized by heterotopic ossification of soft tissue. The condition is predominantly seen in young adults and adolescents and is most commonly secondary to trauma. Although the exact etiology remains unclear, patients typically present with pain and restricted range of motion following trauma or overuse. MO rarely presents in the popliteal fossa of adult patients and has not been previously reported in that of a pediatric patient.

METHODS: We present a 12-year-old patient with no history of direct trauma with MO in the right popliteal fossa, a highly unusual location. Initial x-rays failed to show the lesion; however, later radiographs showed an ossified mass. At peak dimensions, the ossification measured 3.8 cm anteroposterior×2.5 cm transverse×3.2 cm craniocaudal. After 14 months of observation and conservative therapy, the mass was excised.

RESULTS: The patient was ultimately able to return to full activity. Radiographs taken 14 months after the excision showed no signs of recurrence of the lesion.

CONCLUSIONS: To our knowledge, this is the first reported case of MO excised from the popliteal fossa of a pediatric patient and followed for >1 year.

LEVEL OF EVIDENCE: Level IV-case report.