Cortisone is a strong anti-inflammatory medication. A cortisone injection can help with many painful musculoskeletal conditions. The idea behind a cortisone shot is that it delivers a potent anti-inflammatory directly to the site of the pain. Inflammation drives pain, so reducing it can reduce pain quickly.
Cortisone injections may be used for trigger finger, thumb side wrist tendonitis, tennis elbow, hip bursitis, thumb arthritis and arthritis of the knee, to name just a few. When a joint, bursa or tendon sheath is inflamed and irritated, a cortisone injection usually helps the problem right away because it reduces inflammation which decreases pain. For many of these problems, a cortisone shot is often the first recommended treatment before surgery is considered.
The downside: no one knows in advance how long the relief will last, and it differs between patients. A cortisone injection helps control pain, but it does not restore the joint. It will not make worn-away cartilage regrow, and that matters most where arthritis concentrates, knee pain above all. A patient's health and other conditions also shape the response. For example, patients who are diabetic, who have long-standing symptoms, or who have multiple digits involved tend to do worse with injections for trigger fingers. On the thumb side of the wrist, the tendon anatomy itself sometimes blocks the injection, rather than the steroid failing. None of that argues against the injection; it argues for realistic expectations. How many shots came before also matters: a fourth injection is a very different decision from a first. Steroid injections can help, and they can also injure the joint when given again and again.
Steroid injections are also different from steroids taken in pills. Injections deliver the medications to the area locally, but the body absorbs some of the medication systemically. How much steroid reaches the rest of the body, and for how long, depends on what is injected, where, how much, and the patient's overall health. Whether an injection is risky for you specifically is your prescriber's call, not this page's.