Synovial tissue volume shrinks following intra-articular steroid injections and rebounds after a pain relapse, researchers report.
The research team led by Terence O’Neill from Arthritis Research UK Centre for Epidemiology in Manchester, UK say their findings suggest that synovitis should be considered a treatment target for symptomatic knee OA.
Their open label study of 120 people with symptomatic knee OA used contrast enhancement to quantify synovial volume on MRI immediately before an intra-articular steroid injection and 20 days after.
They found a significant improvement in knee pain and a reduction in STV following the steroid injection, with a significant correlation between change in pain and change in STV.
Among those whose pain recurred within 6 months both pain and STV increased, they reported in the Annals of the Rheumatic Diseases.
A significant correlation was observed between increasing pain and increasing STV when patient and time effects were adjusted for.
“Our data suggest that synovitis can be considered a candidate treatment for anti-inflammatory therapies in knee OA which focus on their analgesic effect,” they concluded.
However they noted that the study had several limitations, including the fact that subjects were aware of the intervention.
“Consequently it is not possible to isolate the effect of the intervention on symptoms or structural outcomes as would be possible in a placebo controlled trial,” they said.
The stats:
Overall 85/120 (71%) of the patients were OARSI responders. Pain decreased (mean change in KOOS=+23.9 p<0.001) following steroid injection, as did mean STV (mean change=−1071 mm3; p=0.01).
Of the 80 who returned for a third MRI, pain relapsed in 57, and in the 48 of those with MRI data, STV increased between follow-up and final visit (+1220 mm3; p=0.05).
When the researchers controlled for variation over time they found a significant association between synovitis volume and KOOS pain (b coefficient—change in KOOS pain score per 1000 mm3 change in STV=−1.13; p=0.003), although STV accounted for only a small proportion of the variance in change in pain.