Steroid injection into the sacroiliac joint has been proven diagnostic in showing whether or not that’s the source of back, buttock, and/or leg pain. If the injection reduces pain by more than 50 per cent, the treatment is considered successful and confirms the source of the pain as being the sacroiliac joint.
But as with any test, it is possible to have a false positive or false negative response. In the case of a false positive test, the patient gets better but not because there was a true sacroiliac joint dysfunction that responded to the antiinflammatory/numbing agent. That’s why a second injection may have no effect.
In the case of a false negative, the first injection failed to change the patient’s pain, so it was thought that the problem wasn’t in the sacroiliac joint when it really was the culprit.
There are other factors to consider when evaluating the effectiveness of steroid injections into the sacroiliac joint for control of back, buttock, or leg pain. The results of a recent study of patients with sacroiliac joint dysfunction but without spondyloarthropathy (underlying inflammatory cause) may help.
Those who were treated with steroid injections found that having a lumbar or lumbosacral fusion could hamper the results. Those patients were less likely to get better or have a sustained (more than six weeks’ long) period of pain relief.
So, there may be an explanation for your situation. But it can be a very individual and variable reason for the outcome. Some say don’t bother having the second injection if the first didn’t work. Others want to test the theory that it was a false negative and that a second (or even third) injection is still reasonable. Your physician may have some additional insight to offer based on your history and clinical exam. Don’t hesitate to bring this up for discussion.