The validation of simple scoring methods for evaluating compartment-specific synovitis detected by MRI in knee osteoarthritis

Objectives. Synovitis is common in osteoarthritis (OA) of the knee. In order to evaluate its importance, valid and reliable quantification methods are required. The aim of this study was to compare simple, semiquantitative synovitis scores with detailed volume assessments in subjects with knee OA using magnetic resonance imaging (MRI) as the investigative tool. Methods. Thirty-five subjects with clinically diagnosed OA of the knee were assessed for synovitis using gadolinium-enhanced MRI. The volume measurement of synovitis was assessed at four sites (medial and lateral parapatellar recesses, intercondylar notch and suprapatellar pouch). The semiquantitative scoring of synovitis was scored on a 0-3 scale. Establishment of a correlative relationship was undertaken using Spearman's rho for the individual site-specific measurements. Ordinal regression modelling was undertaken in order to establish the capacity of the synovitis scoring to predict the volume measurement. Results. A total of 140 sites were assessed. There were good correlations between the semiquantitative scores and the volume measurements, ranging from rho = 0.86 (P < 0.00) for the medial parapatellar recess to rho = 0.71 (P < 0.00) for the lateral parapatellar recess. The ordinal regression suggested that, while the synovitis scores predicted between 50 and 70% (R-2 = 0.53, P < 0.00 to R-2 = 0.71, P < 0.00) of the volume measurements, there was some minor overlap, particularly in the mid-range synovitis scores. Conclusions. These results suggest that semiquantitative synovitis scores are valid and will enable feasible evaluation of the synovium in OA cohorts.