A 38-year-old patient complains of pain in the lower back and left knee and ankle joints. Blood test results were as follows: leukocytes 11-109/L, ESR-38 mm/hour, CRP ++, ASL-O titer 125 units, uric acid 375 memol/L, rheumatoid factor negative. Chlamydia were detected in the urethral swab. X-ray shows that the articular surfaces on the left are uneven, indistinct, the joint space is narrowed. What is the most likely diagnosis in this case?