Objective To investigate the relationship between MRI findings and clinical pathological features of pigmented villonodular synovitis of the knee. Methods MRI and pathological data of 21 patients with PVNS in our hospital from 2014 to 2017 in January were retrospectively analyzed, and the relationship between MRI features and clinical pathological features was analyzed. Results Among 21 cases of PVNS, there were diffuse type in 17 cases, and localized type in 4 cases. The pathological features of PVNS showed irregular diffuse or nodular hyperplasia of the synovial membrane, which could be seen in the presence of a large number of blood vessels and nodules containing a large number of blood stasis, adjacent meniscus or (and) bone erosion and joint effusion. MRI imaging: all patients showed different degrees of intra-articular effusion, 17 cases of diffuse type, and synovium showed diffuse nodular thickening. T2WI showed slightly higher signal, T1WI showed low signal, hyperplasia nodules showed nodular or punctate T2WI showed low signal, T1WI showed low signal. 2 cases showed obvious enhancement of synovial hyperplasia, and visible nodules showed patchy no enhancement area. 15 cases of patella fat pad invasion, the infrapatellar fat pad showed irregular morphology. 8 cases of knee joint articular cartilage damage. 4 cases of localized type, visible synovium and tendon sheath and nodular soft tissue signals were closely related soft tissue, and T1WI and T2WI showed visible signs of patchy low signal intensity. Conclusion MRI can reflect the pathological basis of PVNS, and it has high application value in the diagnosis of PVNS