Low back pain's etiology (cause) is one great example of the seeming impenetrable nature of reality. Is back pain caused by mechanical failure of discs and boney joints? Or is it caused by hypersensitivity in spinal nerves due to chemicals present with inflammation? Or is low back pain caused remotely by the body's executive center--the brain? Undoubtedly all these tissues and organs take some role in all back pain. But to definitively identify the one tissue or one organ which is principally responsible for back pain in a particular patient is unreasonable.
For example, I recently treated a woman who was diagnosed with a right groin strain. She has a history most significant for leukemia and treatment by radiation and stem cell transplant. Upon evaluation I noted that she was tender to touch over her pubic bones, her groin muscles and her outer hip muscles. Additionally when I had her lie on her back and applied a posterior (backward) shear stress through her right hip joint she complained of increased groin pain. I was immediately concerned about three things:
1) Possible stress fracture in her right hip which would occur due to post-menopausal osteoporosis;
2) Possible cancer metastasis to her pelvic girdle;
3) Possible low back pain referred to the right groin.
Her doctor ordered an MRI of her hips which revealed mild arthritic changes in both hips. Previous MRI of the lumbar spine had revealed mild spondylolisthesis (miniature spine fractures with no to minimal spinal bone displacement) at L4-5 and L5-S1. This data discourages the view that hip fracture is the cause (although MRI's can miss stress fractures) and ruled out a bone tumor. Possible causes of her hip pain would then be:
1) Mild hip arthritis;
2) Referred low back pain;
3) Muscle weakness and imbalance.
The doctor injected her outer hip area with carbocaine (a medicine in the lidocaine family) which immediately relieved that pain. The doctor ruled out low back pain at that point, stating that if it were low back pain the carbocaine would not have helped. Reflecting back on this just now I would beg to differ with his conclusion. Low back dysfunction causes hypersensitivity in sensory nerves distal to the low back. If her tender outer hip is caused by hypersensitive sensory nerves (versus a traditional bursitis or tendonitis) then carbocaine would have the affect of "numbing" these hypersensitive sensory nerves and render them inactive thus blocking the patients outer hip tenderness. In which case her hip pain would be from her back and not from her weak hip.
Medical professionals could spend a lifetime studying this patient and patients like her and may still be unable to determine which tissues or organs are responsible for her pain. Regardless of if we could identify whether it was the patient's back or hip or muscles which are causing her pain the causal question remains unsatisfactorily answered. For instance, if we determine it is muscle weakness on the right side causing her pain we do not definitively know what caused her right hip weakness. Why are both hips not weak? Why does a very active person who regularly exercises have this mysterious unilateral weakness? If we determine that it is her back causing the pain we do not definitively know what it is that causes her back pain. Is it her facet joints? Is it her disc? Is it her spinal nerves? Or, to beat all, is it because she has had this mysterious chronic weakness in the right hip?
And so it goes for the man asking the 'why' and 'how' questions. Just when he thinks he has gained some understanding he realizes that he has merely unearthed ten more questions about the nature of reality.
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