The patient's presentation is most likely consistent with reactive arthritis, given onset of asymmetric arthritis and extra-articular manifestations (e.g. mouth ulcers) in the setting of a recent genitourinary infection. The first line therapy for reactive arthritis are NSAIDs, making answer 1 the most appropriate choice.
Reactive arthritis (also known as Reiter's Syndrome) is an aseptic inflammatory polyarthritis. It classically presents with urethritis, conjunctivitis/uveitis, and arthritis ("can't see, can't pee, can't climb a tree"). However, not all of these symptoms need to be present to make a diagnosis. Additionally, other findings may be present, such as mucocutaneous lesions (e.g. mouth ulcers), Achilles tendon pain (enthesitis), and a "sausage digit" (see illustration A). Thus, one should suspect reactive arthritis when a patient presents with asymmetric oligoarthritis and any of these extra-articular manifestations. Synovial fluid analysis is usually sterile in reactive arthritis.
Reactive arthritis shares similarities to gonococcal arthritis. However, as Barth and Segal note, arthritis caused by gonorrhea is more acute, migratory in nature, and frequently occurs in the presence of a pustule with an erythematous based on the hand or foot.
As Keat notes, reactive arthritis usually follows nongonococcal urethritis or infectious dysentery.
Illustration A shows a "sausage digit" commonly associated with reactive arthritis.
Answer 2: Methotrexate is used most commonly for rheumatoid arthritis, not reactive arthritis.
Answer 3: Although synovial fluid cultures are frequently negative in gonococcal septic arthritis as in reactive arthritis, gonococcal septic arthritis does not usually have extraarticular manifestations like mouth ulcers or enthesitis. Also, patients are generally febrile gonococcal arthritis.
Answer 4: Colchicine is used in the treatment of acute gout.
Answer 5: Allopurinol is used to prevent gout in patients with hyperuricemia.