bone, joint, and muscle disorders
Infectious Arthritis
Diagnosis of Infectious Arthritis
Analysis and culture of joint fluid Blood tests Sometimes sputum, spinal fluid, and urine tests Sometimes x-rays, magnetic resonance imaging (MRI), or ultrasonography Doctors typically suspect the diagnosis of infectious arthritis in people who have severe or unexplained arthritis and in people who have other combinations of symptoms that are known to occur in people who have infectious arthritis. Usually, a sample of joint fluid is removed with a needle (called Joint aspiration (arthrocentesis) , or arthrocentesis) as soon as possible. It is examined for an increased number of white blood cells and tested for bacteria and other organisms. The laboratory can usually grow and identify the infecting bacteria from the joint fluid (called a culture), unless the person has recently taken antibiotics. However, the bacteria that cause gonorrhea, Lyme disease, and syphilis are difficult to recover from joint fluid. If bacteria do grow in culture, the laboratory then tests which antibiotics would be effective. A doctor usually does blood tests because bacteria causing joint infections often appear in the bloodstream. Sputum, spinal fluid, and urine may also be tested for bacteria to help determine the source of infection and determine whether the infection is anywhere else. If doctors suspect the infectious arthritis is caused by Gonorrhea , samples are also taken from the urethra, cervix, rectum, and throat. Tests for To make the bacteria easier to detect and identify, doctors may analyze the joint fluid using the polymerase chain reaction technique (a type of nucleic acid amplification test [NAAT]) to detect the DNA of gonococci and mycobacteria. Doctors may take X-rays of the affected joint to rule out other conditions. Doctors may do 