Rheumatoid arthritis (RA) is a systemic autoimmune disease involving multiple joints and often involves the small joints, and the lesions are symmetric, invasive, and disabling. Synovial blood flow in patients with RA was compared using color Doppler flow imaging (CDFI), power Doppler ultrasound (PDUS), and superb microvascular imaging (SMI) to determine the application value of SMI in synovial vasospasm of knee joints. The blood flow signals of the suprapatellar recess in the knee joints of 41 RA patients (49 knees) were measured prior to undergoing total knee arthroplasty (TKA), recorded, and graded by CDFI, PDUS, and SMI. The results of the three ultrasound examination methods were compared and analyzed. The SMI grading was compared with the pathologic grade of the synovial membrane. Forty-one patients underwent 49 TKAs. The display rate of the synovial blood flow signal was 93.9% in the CDFI model, 97.9% in the PDUS model, and 100% in the SMI model. There were statistically significant differences in the results between the three ultrasound examination methods (HC = 11.84, P < 0.05). The consistency of the SMI and pathologic grades of synovial membranes was better than the other methods (kappa = 0.639, P < 0.05). Compared with CDFI and PDUS, the signal of synovia flow detected by SMI was significantly higher in RA patients. SMI classification had a better consistency with the pathologic grade, and SMI has application value in assessing the activity of RA.