Could you tell me what happens after a cortisone shot is injected into the shoulder?

Calms inflammation.: Nobody uses cortisone anymore unless you are a horse. Everyone knows what it is though so we usually call steroid injections "cortisone". This is essentially equivalent to putting Ibuprofen right at the source of the inflammation. The inflammatory response is a chain reaction in our body. Steroid works a bit higher on the sequence of reactions and stops the inflammatory response.