Localized pigmented villonodular synovitis in an unusual location in the knee.

PURPOSE: Localized pigmented villonodular synovitis (LPVNS) is a rare lesion that can affect any joint, although it is most frequently found in the knee. Clinically, it is difficult to diagnose. Radiographs are usually within normal limits.

TYPE OF STUDY: Case series.

METHODS

We present a series of 9 cases of LPVNS of the knee in 9 patients with an average age of 36 years. In 7 of the 9 cases, the lesions were in an an unusual location, 4 in the fat pad and 3 in the posterior compartment of the knee. The other 2 cases were located in the meniscocapsular junction and the intercondylar notch, respectively. The mean time from the onset of symptoms to diagnosis was 2.26 years. Magnetic resonance image (MRI) provided a characteristic image that helped with diagnosis and localizing the lesion in all cases.

RESULTS

Complete resection of the lesion using arthrotomy was performed in 4 cases and resection assisted using arthroscopy was performed in 5. All cases had an excellent result. There were no signs of clinical or MRI recurrence after a mean follow-up of 36 months.

CONCLUSIONS

LPVNS of the knee is a rare lesion. MRI provides the basis for diagnosis. Complete resection using arthrotomy or arthroscopy is the treatment.