A question about the anatomy of my lower back, and my one tiny symptom of possible back problems that has caused much worry on the part of my girlfriend...
I have, over the past five-ten years, noticed what feel like lumps in my lower back. These have not concerned me much, mostly because I have had very few symptoms that point to a back condition. I do not suffer from regular back pain or any problems of that nature. I should note that I am overweight, and probably classifiable as obese at this point in my life. Still, these lumps are not unique or strange in that they are uniform on each side of my spine. I have been looking at anatomy charts and diagrams trying to verify that they are indeed normal. So that is my question today, are these ridges/lumps in my lower back normal or should I worry that they are tumors or some problem? Please read the descriptions below...
I will give you some background as to how I wound up on this site. My girlfriend is concerned about these lumps, more so lately because I have had a recent spot of numbness of the skin on my left thigh. She is working on a Masters in Biology and she has pointed out that numbness of a patch of skin on your thigh is usually caused by a joint problem or a lower back problem such as pressure on a nerve. I have contested that my research concerning numbness in the thigh does point to pressure on a nerve in the lower back, but most of the time it is caused by normal wear and tear the same as stiffness. Such numbness can come and go, and it is especially common in fat or pregnant people. I am willing to admit that I am fat
I have not been worried about the lumps in my back because they seem to me to be part of my body, as strange as that might sound. I have pushed, pulled, and kneaded them daily for the past few years and they are more like ridges than lumps. They don't seem to be growing or changing. They are uniform on both sides of my spine in my lower back. The lowest ones, near my hips, are larger and the next two pairs and they become progressively smaller as I follow them up towards my middle back, much like the vertebrae of the spine seem to do in an anatomy chart. I don't think they are the bone of the vertebrae, and I am not even sure that they are attached to the bone of my spine directly. Still, I have assumed that these lumps are part of my spines natural structure. I have perfect range of motion in my back. For a chubby guy I move fast and I can bend, lift, push, pull, and otherwise move as much as anyone my age. I have experienced neither weakness nor stiffness that seems abnormal. I just happen to have noticed two sets of three lumps, one on each side of my lower spine that I can't seem to place on a picture of the spine. I can feel them through my skin, they don't hurt, they move a little like cartilage, and for the most part they seem to be there to support my weight. I cannot stress enough that they are the same on each side, and they almost seem to compliment each other. If I had to guess I would say they are bulging part of my normal spine, if they are abnormal at all.
I am hoping that my description above and below will allow someone to agree that they are normal, or at least not some serious abnormality. Someone out there is bound to know more about the spine's structure than I do. My girlfriend is only a first year MS so she hasn't gotten into heavier anatomy yet, just the basics. I have found the basics online and all diagrams seem to show the same thing. They aren't really helping me to determine if the lumps are normal or not. I can guess that they are any number of things based on the descriptions in the diagrams, but I really don't know. Ironically, I can't push on my girls back to find out of she has similar bumps because she suffers from serious lower back pain

Who should be seeing a doctor here? I digress...
There are no lumps/ridges in my middle back at all. As I have said, the ones in my lower back are uniform in size and shape, and they exist on both sides. They are not really hard, they are more like cartilage. When I push on them I can move then around a little, just a little. They seem to move with the surrounding muscle, i.e. they are flexible enough to move and not stiff. They do not hurt, and I have had no real symptoms of back pain other than normal stiffness if I bend and lift a lot during a day. They are not sensitive to my touch.
I have tried to verify what they might be, normal or not, based on research. I assume that they are normal because all of the other abnormal things that they could be do not match their description in one fashion or another. Things such as spinal tumors and diseased nerves. My research on tumors shows that they usually occur on one side or the other or in the middle on the spinal cord itself. That description seems pretty far from what I have going on in my back. The pictures seem even further from anything I am detecting in my own body. I think it is general common sense that tumors aren't something that happen in any sort of order or perfect shape.
I have also read that disc bulges and the hardening of bones and tissues are common signs of age in the lower back. The above aging symptoms begin to happen as early as your twenties, and I am 30 now so I have been expecting my body to start showing its age.
As far as my slight numbness, most of the information I have found about leg numbness agrees that it is common and usually goes away. It is most commonly a symptom of pressure on a nerve. It is quite common in overweight people and pregnant women, but it can happen to anyone if they stress their back. My numbness is only on a small patch of skin on my outer left thigh. It has happened to me before, in the past, after standing all day. Recently it seems to have lingered longer than usual, but it was never really completely numb and it has already gone away. It lasted about a week and had been apparent since the week prior when I was moving around a lot, much more than normal. I have been under the impression that the numbness was normal and that it was a result of my increased activity. Does that sound like a fair self-diagnosis?
Bottom line, should I be concerned? I would really like to hear from anyone who has similar lumps or knows about such things. I plan to see a doctor, just to be sure of what is going on, I just want to be prepared for whatever possible diagnosis. I like to go into a doctor's office feeling as though I have informed myself as much as possible. I don't like too much surprise, and at this point I think it would really shock me if these were not normal. Regardless, I want to be able to all but rule out any serious issue since these don't seem serious. If I were hurting or limping around I would worry, but I feel great. I just happen to not know about a part of my anatomy that I have detected. The only real symptom I have that might point to a "problem" in my opinion is the slight numbness, and if it is really that common how can it be conclusive.
Any opinions? Advice?, other than see a doctor
Any information will be much appreciated. Thank you.