Infantile hemangiopericytoma is an uncommon cause of a soft-tissue mass in the neonatal period. Only 86 of these tumors have been reported in the literature. Thirty of these were located in the extremities. This review presents a case of infantile hemangiopericytoma localized to the knee in an 8-month-old infant. Current literature suggests that the majority of these lesions are benign, and surgical excision is curative. Recurrence and metastatic disease rarely occur. Because 30-50% of infantile hemangiopericytomas occur in the extremities, orthopaedic surgeons should be aware of and familiar with this tumor.