Intra-articular angioleiomyoma of the knee with an atypical finding on gadolinium-enhanced magnetic resonance imaging: a case report

INTRODUCTION Angioleiomyoma is a benign smooth muscle tumor. It originates in the tunica media of veins. In general, it arises from the dermis, subcutaneous fat and fascia of lower extremities in middle-aged women. The case of intra-articular occurrence is very rare. CASE PRESENTATION This case report describes a 30-year-old Asian man with a 6-month history of recurrent pain localized in the lateral side of his left knee. Magnetic resonance imaging revealed an isolated intra-articular lesion. We performed a surgical excision of this lesion. On histological examination, the diagnosis of angioleiomyoma was confirmed. After the surgery, he recovered completely. Furthermore, no sign of recurrence was observed 1 year after surgery. CONCLUSIONS In this study, we report a rare case of intra-articular angioleiomyoma of the knee. The mass showed atypical findings on magnetic resonance imaging including gadolinium-enhanced imaging in comparison to previously reported intra-articular lesions. This intra-articular tumor is difficult to diagnose prior to surgery due to paucity of information.