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.
A small and very rare risk is that the injected joint becomes infected (1 in 15,000). Patients who experience a very painful, red, or swollen joint after injection should seek medical attention immediately. Thankfully, the most common cause of these symptoms is not a concerning infection but a reaction to the injected steroid (called steroid flare ) that occurs in 2-5% of patients. A steroid flare usually begins 6-12 hours after the injection and can last for 2-3 days. Regardless of the cause, it is important for patients with symptoms of infection to see a doctor because infections require immediate treatment.