The objective of the study was to evaluate cytokine concentration and profile of lipid peroxidation in synovial fluid of patients with osteoarthritis and concomitant defects of articular surfaces. Material and methods Synovial fluid samples were taken from 102 patients with osteoarthritis of the knee joint. Patients with rheumatoid arthritis, osteoarthritis of a post-traumatic etiology, and somatic diseases that could affect results of the study were excluded from the study. Thirty control samples originated from deceased donors of both genders. Synovial fluid was extracted in compliance with Ministry of Health Order No. 694 dtd July 21, 1978, p. 2.24 Guidelines of forensic medical examination in the USSR. Results Findings of laboratory studies showed statistically significant differences in synovial fluid cytokine levels depending on absence or presence of defects on the tibial condyles. Biochemical tests revealed greater changes in lipid peroxidation in patients with articular defects. Total level of lipid peroxidation products resulting in the formation of conjugated dienes (CD), malondialdehyde (MDA) was shown to increase in both groups of patients being significantly higher in patients with defects on articular surfaces. Primary (conjugated dienes) and secondary (malondialdehyde) lipid peroxidation products accumulated in the synovial fluid of the patients with the levels being significantly increased in both groups with no changes in the CD/MDA ratio. Patients with defects on articular surfaces demonstrated increased formation of primary products, and non-defect group showed greater formation of secondary products. Antioxidant enzyme, catalase, appeared to me more active in patients of Group I. Conclusion The findings can be used to evaluate defects on articular surface and identify strategies of medication therapy.