Inflamed joints and tendons will often respond positively to injections of cortisone. Cortisone is a naturally occurring substance which the body produces to (amongst other things) damp down inflammatory changes. Drugs like ibuprofen (Brufen) and diclofenac (Voltarol) are prescribed to perform this function, but cortisone (and its derivatives) are many times more powerful. Cortisone would be destroyed by the stomach's acid if swallowed, so the only way to get it into the body is by injection. Injection into the bloodstream would produce effects throughout the body, when a single joint or inflamed tendon is the real target. As a result, targeted injection into the painful zone will produce the greatest effects for a given dose of cortisone - without the side effects of generalised injections into the bloodstream.

Local anaesthetic is often used to make the deeper part of the injection less uncomfortable. The injection of local anaesthetic still requires a small, sterile needle which will be felt as a sharp pin prick. The discomfort of injections is directly related to the speed of injection. A slow, gentle injection should not be particularly uncomfortable.

Sometimes, certain joints or tendons are so small or narrowed by disease that an accurately placed injection is not possible without the help of a scanning or xray machine. Your doctor may ask a radiologist (xray doctor) to arrange your injection using a scanning machine. This ensures accurate placement of the injected solution. If the outcome of the injection is not as favourable as expected, at least it will be clear that the exact location was correct, and repeat injection is unlikely to be effective.

Cortisone injections will usually result in some local increased tenderness and discomfort for up to 48 hours after injection. The injection of fluid stretches what is already a painful area, and this takes time to resolve.

Injections will leave a tender bruised area for no more than a couple of days. When cortisone is injected just under the skin's surface, it can cause localised thinning of the skin and even depigmentation of a small localised area.