Well, it could be muscle spasms; or, there are nerves that run from the spine to different areas of the body and if a disc or something compresses nerve in there somewhere, one can feel pain in far off areas. Like with sciatica, something is compressing a lurabar nerve and it can cause pain, for example, in a line from one's rear end, going down the leg and even into the foot.
I've been having more recent problems where I get severe nerve pains which radiated around my outer hip areas & into the groin, but it didn't go down my leg. But after some time, I started getting nerve pains all over the place, including down the front of one thigh, over one knee, on both sides of both ankles, both tops of feet. So when nerves get compressed in the spine, it can refer pain to other areas. I do know one can feel nerve pain in the thigh from spine problems, but I am not sure about the waist area. Can you describe in more detail where in the thigh & waist your pain is?
