Sandra Leigh Moore MD, Presenter: Nothing to Disclose

Adam C. Zoga MD, Abstract Co-Author: Nothing to Disclose

Mark E. Schweitzer MD, Abstract Co-Author: Nothing to Disclose

Lyme arthritis most often involves the knee, and may mimic other inflammatory arthridites. We sought to determine if characteristic MR findings exist for Lyme disease of the knee.

Retrospective evaluation of knee MRIs of 6 patients with clinically proven Lyme disease (M 4, F 2, average 33 years) was performed by 2 MSK radiologists by consensus. Routine knee protocols were used. The readers assessed for the location and extent of marrow edema, erosions, cysts, cartilage tears, osteophytes, synovial proliferation, effusions, enthesopathy, and regional lymphadenopathy. Correlation was made with MRI studies of 8 patients with rheumatoid arthritis of the knee.

Osseous changes: 5/6 subjects had erosions (3 MFC, 3 MTP, 1 LTP, 2 trochlea). Marrow edema and subchondral erosions were seen at bare areas in 2. No subchondral cysts were seen. The patella was spared in 5/6. Four patients showed cartilage insults. 1/6 subjects had osteophytes. Synovial changes: 6/6 subjects had synovial thickening up to 3 mm, and large suprapatellar effusions containing debris. One had a ruptured popliteal cyst, one fluid in the pes anserinus bursa. Five had subpopliteus bursa effusions, and one large popliteus tendon sheath pannus. Five had synovitis in Hoffa's fat pad. 5/6 subjects had large popliteal fossa lymph nodes.

MRI of Lyme arthritis of the knee shows findings in common with rheumatoid arthritis including bare area erosions, marrow edema, and synovial proliferation. The paucity of patellar cartilage involvement, popliteus fossa lymphadenopathy, and involvement of posterior lateral synovial spaces may be distinguishing features.

Moore, S, Zoga, A, Schweitzer, M, Characteristic MRI Patterns of Lyme Arthritis of the Knee.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4414966.html