Objective To compare the advantages and disadvantages of MRI and arthroscopic diagnoses of gout arthritis of the knee joints. Methods The MRI and arthroscopic images of the knee joints in 30 patients were compared and analyzed. The patients were confirmed by pathological examination to have gouty arthritis. The advantages and disadvantages of MRI and arthroscopy in diagnosis of gout arthritis were compared. Results There was no significant difference between MRI and arthroscopy in the diagnosis of the lesions in the joint cavities of the patients with knee gout arthritis, and MRI was significantly better than arthroscopy in diagnosis of the lesions outside of the knee joint cavities. Conclusions There is no significant difference between MRI and arthroscopy in the diagnosis of the lesions in the joint cavities of the patients with knee gout arthritis, and MRI is significantly better than arthroscopy in diagnosis of the lesions outside of the knee joint cavities. The combination of the two can make better diagnosis of gout arthritis.