Clinical meaning
Low back pain (LBP) originates from the complex interplay of spinal structures in the lumbar region (L1-L5 vertebrae and the sacrum). Pain generators include the intervertebral discs (annular tears allow nuclear material to irritate sinuvertebral nerves; herniation compresses nerve roots), facet joints (zygapophyseal joints with richly innervated capsules that develop osteoarthritis with aging), paraspinal muscles and ligaments (strain from acute injury or chronic postural stress), sacroiliac joints (inflammation or dysfunction producing referred pain to the buttock and posterior thigh), and the spinal canal (central stenosis compresses the cauda equina; lateral recess stenosis compresses individual nerve roots). The intervertebral disc consists of the nucleus pulposus (gelatinous core that absorbs compressive loads) surrounded by the annulus fibrosus (concentric rings of collagen fibers). With aging and repetitive loading, the nucleus pulposus loses water content and proteoglycans (disc desiccation), the annulus develops circumferential and radial tears, and the disc height decreases -- this cascade is termed degenerative disc disease. When nuclear material herniates through annular tears and contacts the dorsal root ganglion or nerve root, it produces radiculopathy through both mechanical compression and chemical...