Are there ever false negative results from an SI injection?
When a physician gives an injection directly into the sacroiliac joint, about the only time it gives relief is when there are tears in the joint capsule and the anesthetic leaks out to the adjacent tissue. If there are no tears then the anesthetic is held within the joint capsule and will not give any relief. This is a false negative test. It is better to give the injection into the area of the posterior inferior iliac spine which is just posterior to the SIJ. Look for a trigger point in that area.
