Background. Chronically progressive course of psoriatic arthritis, not the certainty of pathogenetic units, and accordingly errors in diagnosis and treatment lead to significant negative results and disability of patients. Objective is to improve the results of the diagnosis of PA by examining the morphological features of the disease. Methods. Histomorphological studies performed on tissues removed during surgery on the joints in 32 patients. The material distributed into groups depending on the severity of the clinical manifestations of the disease. Results. At the beginning of the disease and at the exudative-proliferative stage, a pattern of pronounced inflammatory process, mainly exudative, serous-fibrinous character, was noted in the capsule of the joint. The most significant changes occurred in the synovial membrane, where marked proliferation of the integumentary synovial cells, hypertrophy and hyperplasia of the synovial membrane were observed with the formation of a large number of villi and folds. At histological examination in the tissues of the joint with a dystrophic-degenerative stage there was a pronounced exudative-proliferative inflammatory process, with significant degenerative-dystrophic and fibro-sclerotic changes. Conclusion. Histological studies in patients with PA, evidence of the presence of a sharp non-specific, non-peculiar, non-peculiar, non-peculiar, non-peculiar, non-peculiar, non-peculiar, syllabic history changes. Pathological changes in the articular cartilage and subordinate epiphysis bone are manifested by significant degenerative-dystrophic and destructive manifestations.