Cortisone injections are among the most commonly used treatments in orthopedics. Cortisone is a powerful anti-inflammatory medication that reduces the inflammatory response of many painful conditions. Cortisone is effective for different types of arthritis, tendinitis, and bursitis, among other conditions. It is often used as a first line of defense to diminish the immediate pain and inflammation of arthritic joint. Although the effect of cortisone is temporary, reducing pain and inflammation may give the joint a chance to compensate in other ways. Therapy tends to be more effective under comfortable conditions.

Cortisone is a powerful anti-inflammatory agent which minimizes the production of inflammatory cascade that occurs within the joint. At the basic science level, there are a number of mechanisms by which the improvement is thought to occur - mRNA synthesis, B and T cell function, cytokine levels, metalloproteases and synovial permeability (Creamer 1997, Genovese 1998). The benefits of corticosteroids may also be due to relief of effusions from aspiration and disruption of adhesions within the joint.

The guidelines on knee pain from the American College of Orthopedic Surgeons (1999) and the National Institute for Health and Clinical Excellence (2007) also recommend use of intra-articular steroids in patients with osteoarthritis of the knee that fail to respond to more conservative measures (e.g., NSAIDS or acetaminophen, physical therapy, decreased activity). According to the literature, patients with joint effusions and local tenderness benefit from intra-articular steroid injections.

• Depending on how quickly the inflammation subsides, timing of pain relief can vary from a few days to a few weeks.
• The response to cortisone is variable.  In mild conditions, a single shot can be extremely long-lasting. 
• Some patients may have a reaction to the cortisone injection called a 'cortisone flare.' A cortisone flare is a condition where the injected cortisone crystallizes and can cause a brief period of pain, worse than before the shot. This usually lasts a day or two and is best treated by icing the injected area.

A single cortisone shot is rarely harmful. Disadvantages of cortisone injections depend on the dose and frequency of the injections. With higher doses and frequent administration, potential side effects include thinning of the bones (osteoporosis), and a rare but serious damage to the bones of the large joints (avascular necrosis). Side effects such as these are rarely seen.

There is a risk of local tissue atrophy and depigmentation, particularly when small joints are injected with potent corticosteroids. Concern about progressive joint damage following repeated corticosteroid injections is controversial; despite the large number of people treated with intra-articular corticosteroids, case reports that suggest this may result in joint damage are rare (SCHIN, 2002). According to available literature, it is inadvisable to treat patients with a complete collapse of joint space or bone loss with intra-articular hyaluronic acid or corticosteroids, given their poor clinical response (Evanich, et al., 2001).

The more common issue is the "band aid effect", which is that the cortisone injections obscure are underlying problem that is treatable through other means. Occasionally, there are allergic reactions to cortisone, usually manifesting as facial reddening or sunburn.