Objective. To evaluate the use of routine MR imaging sequences in detecting
and characterizing secondary reactive synovitis of the knee joint using ar
throscopy as the standard of reference.
Design and parents. Fifty consecutive patients with a history of knee pain
who were referred for MR imaging and subsequently underwent arthroscopy of
the knee comprised the study group. MR images were evaluated for the presen
ce and appearance of synovitis reflected in synovial thickening and irregul
arity. Synovial thickening was graded on MR imaging as follows: 0=normal, 1
=thin line of increased signal intensity, 2=increased signal intensity with
frond-like or hair-like projections and a granular appearance of joint flu
id. Standard knee imaging protocols were used.
Results. The sensitivity, specificity, and accuracy of MR imaging in detect
ing synovitis compared with arthroscopy were 88%, 97%, and 95%, respectivel
y. Grade 1 synovitis was best seen on proton-density-weighted images, demon
strating increased signal intensity of the synovium against the relatively
low signal intensity of the joint fluid. Grade 2 synovitis was best seen on
proton-density images and T2-weighted spin echo and fast spin echo images
with fat saturation, demonstrating a granular and linear hair-like appearan
ce of joint fluid. Axial and sagittal imaging planes were most helpful in t
he diagnosis of synovitis.
Conclusion. Routine MR pulse sequences are useful in identifying the presen
ce and extent of synovial abnormalities. The detection of different stages
of synovial pathology should become an important part of the evaluation of
the post-traumatic patient as treatment may be altered as a result.