MSFinals-2565

A 28-year-old man presents to his GP with complaints of joint pain and swelling, feeling generally unwell. He recently returned from a hiking trip in Thailand, and one day after his return, he experienced severe watery diarrhoea and abdominal cramps that lasted for a week.

Upon examination, the patient appears fatigued and unwell. He has large effusions of the left knee and right ankle, along with tender plantar fascia bilaterally. Additionally, he has tender metatarsophalangeal joints on both feet and a papular rash on the soles of his feet. Despite taking regular paracetamol and ibuprofen for the past week, he has experienced minimal improvement in symptoms.

What is the most appropriate next step in managing this patient, given the most likely diagnosis?