What is a common musculoskeletal manifestation of reactive arthritis?

Enthesitis is a common musculoskeletal manifestation of reactive arthritis and is characterized by inflammation at the sites where tendons and ligaments attach to bone. In reactive arthritis, which often follows an infection (commonly genitourinary or gastrointestinal), this inflammation can lead to pain and tenderness in these areas. The presence of enthesitis correlates with the clinical patterns observed in reactive arthritis, making it a significant and distinctive feature of the condition.

Other choices reflect conditions or manifestations not specifically associated with reactive arthritis. For instance, arthralgia, though it can occur in the context of many rheumatological conditions, is a more general term referring to joint pain rather than a specific manifestation. Osteoarthritis is a degenerative joint disease linked to age and wear and tear rather than a post-infectious inflammatory reaction like reactive arthritis. Rheumatoid nodules are associated with rheumatoid arthritis, an entirely different autoimmune condition, and are not a typical finding in reactive arthritis. Thus, the specificity of enthesitis to reactive arthritis underlines its significance as the correct answer.