Imaging Quiz Question

A Medial Soft-Tissue Mass of the Knee

John Lin, MD; Christine Chang, MD

THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 10 - OCTOBER 1, 1999

A 46-year-old man presented to a sports medicine clinic with medial left knee swelling that had begun 2 months earlier after a direct blow from a fall. The patient complained of stiffness and discomfort that occurred with immobilization and resolved with stretching and exercise. He reported no locking or instability. A physical examination showed marked swelling over the medial knee joint line; the area was firm, rubbery, and nontender. There was no suprapatellar effusion. The patient's knee had a full range of motion, and hamstring and quadriceps strength was normal. Magnetic resonance imaging (MRI) was ordered to exclude a soft-tissue tumor (figure 1).

What is your diagnosis, and what treatment would you recommend?

Dr Lin is a clinical assistant professor in the department of radiology at the University of Michigan Medical Center in Ann Arbor and a member of the Society of Skeletal Radiologists. Dr Chang is a staff physician at the University of Michigan Medical Center and St Joseph Mercy Hospital in Ypsilanti, Michigan; she is a fellow of the American Academy of Pediatrics. Address correspondence to John Lin, MD, The University of Michigan Medical Center, 1500 E Medical Center Dr, TC 2910, Ann Arbor, MI 48109-0326; address e-mail to johnlin@umich.edu.