12 Types of Arthritis and How They Differ

10. Reactive Arthritis - The Post-Infectious Response

Reactive arthritis, formerly known as Reiter's syndrome, represents a sterile inflammatory arthritis that develops following certain bacterial infections, typically involving the genitourinary or gastrointestinal tract. This condition affects approximately 1-3% of individuals following triggering infections with organisms such as Chlamydia trachomatis, Salmonella, Shigella, Campylobacter, or Yersinia species. The arthritis typically develops 1-4 weeks after the initial infection and predominantly affects lower extremity joints in an asymmetric pattern, commonly involving the knees, ankles, and feet. The classic triad includes arthritis, urethritis, and conjunctivitis, though complete triad presentation occurs in only about 30% of patients. Additional features may include enthesitis, dactylitis, inflammatory back pain, and characteristic skin lesions such as keratoderma blennorrhagicum on the palms and soles. Like other spondyloarthropathies, reactive arthritis shows a strong association with HLA-B27, present in 60-80% of patients, which may influence disease severity and chronicity. The condition is typically self-limiting, resolving within 6-12 months, though some patients develop chronic arthritis or recurrent episodes. Diagnosis relies primarily on clinical presentation and history of preceding infection, as there are no specific laboratory tests, though elevated inflammatory markers and HLA-B27 testing may provide supportive evidence. Treatment focuses on symptomatic relief with NSAIDs and, in severe or chronic cases, disease-modifying antirheumatic drugs such as sulfasalazine or methotrexate.