28th May 2025

A 35-year-old male presents with a swollen right knee.

A 35-year-old male presents with a swollen right knee. There is no history of injury or trauma, and other than a swollen ankle last week which has since resolved, he has not had anything similar previously. He also mentions that he has had a painful and red right eye for the past few days. There has been no known history of diarrhoea, however, he does report some stinging on passing urine.

Synovial fluid culture from his right knee is negative and there are no crystals.

He has had multiple sexual partners over the past six months who are both male and female.

Which sexually transmitted infection is the most likely cause of this syndrome?

Select the SINGLE most appropriate option from the list below. Select ONE option only.