Corticosteroids help fight inflammation, signaled by heat, redness, pain, and swelling in an injured or inflamed part of the body. Corticosteroid shots ease pain faster than anti-inflammatory pills. When corticosteroids are injected into a joint, their effects are mostly limited to that joint. Steroid shots usually last up to one or two months. However, they can last longer, especially when used with other treatments such as physical therapy. Injections for certain conditions, such as acute joint pain, may also last longer. It's best to limit steroid injections to three or four times a year.