Angioleiomyoma of the knee: An uncommon cause of leg pain. A systematic review of the literature

•Angioleiomyoma is a rare benign painful soft tissue tumor, whose subcutaneous location at the knee joint is rare.•The initial presenting symptom for angioleiomyoma of the knee is localized or radiated pain.•In differential diagnosis of angioleiomyoma in the extremities, peripheral nerve sheath tumor should be consider. Angioleiomyoma is a rare benign painful soft tissue tumor, whose knee location is rare. Due its rarity, and not characteristic aspect on MRI the preoperative diagnosis is difficult. We performed a systematic review of the literature, including a case of venous type angioleiomyoma that we have recently managed. A total of 24 published papers with 30 cases (including our illustrative case) were identified and included in our review. The mean patient age was 42.3 years (range18-63). The average size of the lesion was 17.8 mm. The presenting symptom was leg pain in 90% of cases. On magnetic resonance imaging (MRI), the lesion appeared isointense in T1 in 80% of cases and hyperintense on T2 in 90% of cases. Avid homogeneous enhancement after gadolinium administration was detected in 94% of cases. All patients underwent surgery and total resection was achieved in 100% of cases. No recurrence was observed after a mean follow-up of 19.5 months. Angioleiomyoma occurs rarely in the knee and generally is associated with localized or radiating pain. The preoperative diagnosis is difficult also after completion of MRI study and requires high index of suspicion. Angioleiomyoma widens the spectrum of soft tissue lesions of the extremities and should be included in the differential diagnosis of lesions in this area.