The knee joint aspiration and injection refers to placing a needle into a joint cavity to remove fluid for analysis, and to inject medicine for pain relief or treatment of a disease. Sometimes the doctor may only remove fluid from the joint fluid to establish a diagnosis for the collection of fluid. A collection of fluid within the joint is called an effusion, which can recur after removal of a large amount of fluid.
Rarely are infections into the joint introduced or the cartilage surface inside the joint damaged by the needle.
Most people don’t feel pain, and no anesthesia is used. Occasionally, the procedure can hurt if the needle touches the joint surface. Pain occurring hours after an injection may develop from the crystals of medicine but can be prevented by taking ibuprofen.
Usually the medication is a corticosteroid prepared in a form that will stay largely in the joint. Such injections are given to suppress the pain in that joint for many kinds of arthritis. Another type of injection is hyaluronic acid, which is used only for osteoarthritis. Response to the medicine varies. Call your doctor if the pain returns quickly.