How often cortisone injections are given varies based on the reason for the injection. This is determined on a case-by-case basis by the health care practitioner. If a single cortisone injection is curative, then further injections are unnecessary. Sometimes, a series of injections might be necessary; for example, cortisone injections for a trigger finger may be given every three weeks, to a maximum of three times in one affected finger. In other instances, such as knee osteoarthritis, a second cortisone injection may be given approximately three months after the first injection, but the injections are not generally continued on a regular basis.
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