A 25-year-old patient is not married and has sexual relations with several partners. During the last 3 months he noticed a small amount of mucoserous discharge from the urethra. Subjectively: periodical itching or burning pain in the urethra. Two months ago pain in the knee joint developed. Possibility of trauma or exposure to cold is denied by the patient. During the last week eye discomfort is noted - lacrimation and itching. What provisional diagnosis can be made?