We present a case of pathologically confirmed, relatively rare Pigmented Villonodular Synovitis (PVNS). The patient presented with knee and thigh swelling. While initially misdiagnosed, he eventually underwent an MRI and a biopsy. The MRI was helpful but not definitive. The biopsy confirmed PVNS. The patient underwent synovectomy and was subsequently referred for radiotherapy and physical therapy. Post-treatment MRI showed no evidence of disease.