musculoskeletal and connective tissue disorders
Pain in and Around a Single Joint
Key Points
Arthrocentesis is mandatory to rule out infection in acute monoarticular joint pain with joint effusion. Infection is the most common cause of acute nontraumatic monarthritis in young adults, whereas osteoarthritis is the most common cause in older adults. Crystals in synovial fluid confirm crystal-induced arthritis but do not rule out coexisting infection. Do not use serum urate level to diagnose gout. Joint pain that is still unexplained after arthrocentesis and x-ray should be evaluated with MRI to rule out uncommon etiologies (eg, occult fracture, osteonecrosis, pigmented villonodular synovitis) and molecular techniques, such as polymerase chain reaction, should be done to detect the presence of microorganisms. 