In this feature, AAOS Now publishes a series of images, challenging readers to diagnose the condition depicted.

This month’s challenge was submitted by Letha Y. Griffin, MD, of Atlanta, Ga. Dr. Griffin reports that the patient, a 42-year-old woman, had a history of being unable to bend or extend her right knee after squatting. The patient also reported feeling something slip inside her joint. She had no prior history of an injury to the knee.

Physical examination of the right knee found a range of motion of 40° to 90° and diffuse tenderness to palpation about her joint. No knee instability was detected. An effusion was noted within the joint. Routine radiographs were normal. Figures show a sagittal MRI view (Fig. 1), a pathology slide (Fig. 2), and an arthroscopic view (Fig. 3).

What’s your diagnosis?

Fig. 3 Arthroscopic view of the right knee

Larger images (PDF)

Find the answer to this month’s challenge below

Answer
According to Letha Y. Griffin, MD, who submitted the case, the diagnosis is pigmented villonodular synovitis (PVNS)

“On the sagittal MRI, you can see the nodular lesion localized just beneath the fat pad,” she said. “The pathologic diagnosis was PVNS, but at the time of the arthroscopic procedure, no blood was in her joint and only a solitary lesion was found. The remainder of the synovium appeared normal.

“PVNS is believed to be a proliferative disease of synovium,” continued Dr. Griffin. “It is found in two forms—the more common diffuse form and a localized form termed ‘nodular synovitis,’ such as was found in this patient. The diffuse form is often found in large joints such as the knee and the hip, may recur after resection, and can result in permanent joint damage. The nodular form may be less likely to recur following excision of the lesion.”

Send AAOS Now your case
Do you have a challenging case you’d like to submit for publication? Email a short case description and any accompanying images to aaoscomm@aaos.org