Many people who have hip or groin pain could have arthritis in the hip or in the lumbar spine, the lower part of the back. X-rays, while helpful in many cases, often can't help in this situation. However, in order to treat your mother's pain properly, the doctor needs to know where the pain is originating.
A procedure called a fluoroscopically guided intra-articular injection is one way to determine this. By injecting a medication directly into the joint, the doctor can find out if this helps decrease the pain. If the pain does decrease, then the problem is with the hip. If it doesn't decrease, there is a good chance that it is the spine.