Before the steroid medication takes effect, your pain may briefly return. However, this does not mean the block failed. It may take 24 to 72 hours for the steroid or anti-inflammatory medication to begin working. It can sometimes take up to one week for a steroid to take effect. The injection site may be sore for a day or two after the procedure. It is possible that the pain is caused by the needle being inserted into the sacroiliac joint as well as medication that was injected into it. SI joint injections can last from a few days to several months. Additional injections may be recommended if you achieve partial sustained relief following the first SI joint injection.