Which of the following is likely the diagnosis for a young man with acute onset of pain in the elbow and tendon after recent travel and unprotected sex?

The diagnosis is likely reactive arthritis, which is characterized by joint inflammation that occurs as a reaction to an infection elsewhere in the body. In this scenario, the young man's recent travel and unprotected sexual encounters suggest a possible sexually transmitted infection (STI) or another infectious process that could trigger this condition. Reactive arthritis typically presents as acute pain and swelling in the joints, often affecting the knees, ankles, and feet, but it can certainly also involve the elbow, especially in a young male population.

Reactive arthritis is particularly associated with infections such as Chlamydia trachomatis or gastrointestinal infections following dysentery, making it relevant in the context of recent travel and sexual activity. The acute onset of symptoms following such exposures aligns well with the pathophysiology of reactive arthritis.

Other options like rheumatoid arthritis, septic arthritis, and osteoarthritis do not fit as well with the specific situation presented. Rheumatoid arthritis is a chronic autoimmune condition that typically develops gradually, rather than acutely, particularly in a young male. Septic arthritis involves a purulent infection in the joint, which usually presents with more systemic signs of infection, such as fever, and often different patterns of joint involvement. Osteoarthritis is a degenerative joint disease that is unlikely to cause