For most injections, 1 percent lidocaine or to percent bupivacaine is mixed with a corticosteroid preparation. The dose of anesthetic varies from mL for a flexor tendon sheath (trigger finger) to 5 to 8 mL for larger joints. On rare occasions, patients exhibit signs of anesthetic toxicity, including flushing, hives, chest or abdominal discomfort, and nausea. It can take as long as 20 to 30 minutes following the injection for these symptoms to present. For this reason, and to monitor for allergic reactions, patients should be observed in the office for at least 30 minutes following the injection.
Guidelines from the American College of Rheumatology conditionally recommend the use of intra-articular corticosteroid injections for treatment of knee osteoarthritis. 51 The duration of pain relief is one to two weeks in most trials, with a few showing improvements lasting three to four weeks. 60 – 63 Research uniformly supports the safety of intra-articular corticosteroid injections for treatment of knee osteoarthritis; however, these studies are limited by lack of histologic data and poor long-term follow-up. 64 A Cochrane review found weak evidence for the use of corticosteroid injections for the treatment of knee rheumatoid arthritis. 52
Arthrocentesis – Also called joint fluid aspiration, arthrocentesis is removal of joint fluid through a hollow needle inserted into the joint space of the knee. Although the purpose of removing joint fluid from the knee is usually so that it can be tested in the lab, removing excess fluid can also quickly ease pain and swelling. Often after withdrawing fluid, doctors use the same puncture site where the fluid was removed to inject a corticosteroid preparation and/or anesthetic into the knee joint to further relieve pain and inflammation.