Objective
To evaluate the relationships of quantitative and semi-quantitative (SQ) assessments of synovium with knee OA severity by radiographic and 3T MRI findings.
Methods
58 knee OA patients underwent non-fluoroscopic fixed-flexion knee radiographs. Dynamic contrast-enhanced (CE) 3T MRI was performed pre-/post-gadolinium administration to quantify synovial volume (qSV). SQ synovial outcomes were assessed on CE and unenhanced images. Two radiologists scored X-rays using the OARSI atlas; inter-reader agreement was assessed using Kappas and concordance correlation coefficients. Multiple linear and logistic regression analysis was used to assess associations among variables while controlling the effects of age, BMI, gender and meniscal extrusion.
Results
KL grade, diseased compartment joint space width (dcJSW) and diseased compartment joint space narrowing (dcJSN) were significantly associated with synovial proliferation, measured as CE qSV (β = 0.78, p = 0.0001; β = -0.22, p = 0.0003; β = 0.53, p = 0.0001, respectively). Furthermore, qSV strongly correlated with total subchondral BML volume (β = 0.22, p = 0.0003). KL grade, dcJSW, and dcJSN were significantly associated with BLOKS SQ infrapatellar synovitis (OR [95%CI]: 9.05, [1.94,42.3]; 0.75 [0.54,1.03]; 2.22 [1.15,4.31], respectively) and effusion (OR [95%CI]: 5.75, [1.23,26.8]; 0.70, [0.50,0.98]; 1.96, [1.02,3.74], respectively). CE SQ synovitis also significantly associated with KL and dcJSN (β = 0.036, p = 0.0040; β = 0.015, p=0.0266, respectively), and BLOKS synovitis.
Conclusion
Synovitis is a characteristic feature of advancing knee OA stages, and is significantly associated with KL, JSW, JSN, and BMLs. BLOKS synovitis scoring on unenhanced MRI is associated with CE synovitis measures.