Characteristic magnetic resonance imaging entheseal changes of knee synovitis in spondylarthropathy.
OBJECTIVE
To use magnetic resonance imaging (MRI) in patients with rheumatoid arthritis (RA) and spondylarthropathy (SpA) to determine if the primary site of abnormality differs.


METHODS
Twenty patients with recent-onset knee effusion (10 with SpA and 10 with RA) were evaluated using fat-suppressed MRI. Knee joint effusion and synovitis were confirmed using ultrasonography. MRI scans were independently scored by 2 observers who were blinded to the patient's diagnosis.


RESULTS
All 10 of the SpA patients, but only 4 of the 10 RA patients, had focal peri-entheseal high signal (compatible with fluid or edema) outside the joint (P = 0.01). Six of the SpA patients had bone marrow edema that was maximal at entheseal insertions; in 4 cases this was multifocal. No RA patients showed such an abnormality (P = 0.01).


CONCLUSIONS
Prominent entheseal abnormalities on MRI are a consistent feature of new-onset synovitis in SpA, but are a minor feature of RA. This finding has important implications for the diagnosis, classification, and mechanisms of synovitis in patients with SpA.
McGonagle
D
D
University of Leeds, UK.
Gibbon
W
W
O'Connor
P
P
Green
M
M
Pease
C
C
Emery
P
P
D000328:Adult; D001855:Bone Marrow Diseases / Q000000981:diagnostic imaging; D002061:Bursa, Synovial / Q000002:abnormalities / Q000000981:diagnostic imaging; D003238:Connective Tissue / Q000002:abnormalities / Q000000981:diagnostic imaging; D004487:Edema / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D013167:Spondylitis, Ankylosing / Q000150:complications*; D013585:Synovitis / Q000150:complications / Q000000981:diagnostic imaging*