A sample of joint fluid is needed. This may be done in a doctor's office using a needle, or during an operating room procedure. For more information on this procedure, see: Joint fluid aspiration. The fluid sample is sent to a laboratory where it is placed on a special dish and watched to see if bacteria, fungus, or viruses grow. This is called a culture. If such microorganisms are detected, other tests may be done to further identify the infection-causing substance and determine the best treatment. |