musculoskeletal and connective tissue disorders
Evaluation of the Patient With Joint Symptoms
Testing
Laboratory testing and imaging studies often provide less information than do the history and physical examination. Although some testing may be warranted in some patients, extensive testing is often not. Testing includes Blood tests None Imaging studies None Arthrocentesis and Biopsy of bone, synovium, or other tissue is occasionally done. Blood tests should be selected based on history and examination findings. Some tests, although not specific, can be helpful in supporting or excluding the possibility of certain systemic Introduction to Autoimmune Rheumatic Disorders , as for the following: Antinuclear antibodies (ANA) and anti–double-stranded DNA antibodies in Diagnosis (SLE) Rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies in Diagnosis (RA) HLA-B27 in Overview of Seronegative Spondyloarthropathies (eg, with symptoms of inflammatory back pain and normal x-rays, or with unexplained Tests such as white blood cell count, erythrocyte sedimentation rate (ESR), and C-reactive protein may help determine the likelihood that arthritis is inflammatory due to infectious or other systemic disorders, but these tests are not highly specific or sensitive. For example, an elevated ESR or C-reactive protein level suggests articular inflammation or may be due to a large number of nonarticular inflammatory conditions (eg, infection, cancer). Also, such markers may not be elevated in all inflammatory disorders. Imaging studies are often unnecessary. Plain x-rays in particular reveal mainly bony abnormalities, and most joint disorders do not affect bone primarily. However, imaging may help in the initial evaluation of relatively localized, unexplained, persistent or severe joint and particularly spine abnormalities; it may reveal primary or metastatic tumors, osteomyelitis, bone infarctions, periarticular calcifications (as in calcific tendinitis), or other changes in deep structures that may escape physical examination. If chronic Diagnosis , For musculoskeletal imaging, plain x-rays may be obtained first, but they are less sensitive, particularly during early disease, than MRI, CT, or ultrasonography. MRI is the most accurate study for fractures not visible on plain x-rays, particularly in the hip and pelvis, and for soft tissues and internal derangements of the knee. CT is useful if MRI is contraindicated or unavailable. Ultrasonography, arthrography, and bone scanning may help in certain conditions. Arthrocentesis is the process of puncturing the joint with a needle to withdraw fluid. If there is an effusion and arthrocentesis is done correctly, fluid can typically be withdrawn. Examination of synovial fluid is the most accurate way to exclude infection, diagnose Overview of Crystal-Induced Arthritides , and help determine the cause of joint effusions. This procedure is indicated for all patients with acute or unexplained monarticular joint effusions and for patients with unexplained polyarticular effusions. Arthrocentesis is done using strictly sterile technique. Infection or other rash over the site used to enter the joint is a contraindication. Preparations for collecting samples should be made before doing the procedure. Local anesthesia, withlidocaineand/or difluoroethane spray, is often used. Many joints are punctured on the extensor surface to avoid nerves, arteries, and veins, which are usually on the joint’s flexor surface. As much fluid as is possible should be removed. Specific anatomic landmarks are used (see figures,, and). Ultrasound guidance has been shown to increase the likelihood of a successful aspiration. At the bedside, gross characteristics of the fluid are assessed, such as its color and clarity. ). So-called noninflammatory effusions are often mildly inflammatory but tend to suggest diseases such as Osteoarthritis (OA) , in which inflammation is not severe. Laboratory tests commonly done on joint fluid include cell count, leukocyte differential, Gram stain and Microscopic examination of a wet drop preparation of synovial fluid for crystals (only a single drop of fluid from a joint is needed) using polarized light is essential for definitive diagnosis of Diagnosis , The most common crystals seen are those diagnostic of Gout (monosodium urate, negatively birefringent needle-shaped crystals) and calcium pyrophosphate arthritis (calcium pyrophosphate, rhomboid- or rod-shaped crystals that are positively birefringent or not birefringent). If crystals appear atypical in a wet drop, several less common crystals (cholesterol, liquid lipid crystals, oxalate, cryoglobulins) or artifacts (eg, depot corticosteroid crystals) should be considered. Other synovial fluid findings that occasionally make or suggest a specific diagnosis include the following: Specific organisms (identifiable by Gram or acid-fast stain) Marrow spicules or fat globules (caused by fracture) Amyloid fragments (identifiable by Congo red stain) Sickled red blood cells (caused by sickle cell hemoglobinopathies) 