Whether a patient experiences pain or not largely depends on the location of the affected disc and the amount of pressure that is being put on the spinal column and surrounding nerve roots. Nevertheless, degenerative disc disease is one of the most common sources of back pain and affects approximately 30 million people every year. With symptomatic degenerative disc disease, the pain can vary depending on the location of the affected disc. A degenerated disc in the lower back can result in lower back pain, sometimes radiating to the hips, as well as pain in the buttocks, thighs or legs. If pressure is being placed on the nerves by exposed nucleus pulposus, sporadic tingling or weakness through the knees and legs can also occur. A degenerated disc in the upper neck will often result in pain to the neck, arm, shoulders and hands; tingling in the fingers may also be evident if nerve impingement is occurring. Pain is most commonly felt or worsened by movements such as sitting, bending, lifting and twisting. After an injury, some discs become painful because of inflammation and the pain comes and goes. Some people have nerve endings that penetrate more deeply into the anulus fibrosus (outer layer of the disc) than others, making discs more likely to generate pain. In the alternative, the healing of trauma to the outer anulus fibrosus may result in the innervation of the scar tissue and pain impulses from the disc, as these nerves become inflamed by nucleus pulposus material.
As the two vertebrae above and below the affected disc begin to collapse upon each other, the facet joints at the back of the spine are forced to shift which can affect their function.Additionally, the body can react to the closing gap between vertebrae by creating bone spurs around the disc space in an attempt to stop excess motion. This can cause issues if the bone spurs start to grow into the spinal canal and put pressure on the spinal cord and surrounding nerve roots as it can cause pain and affect nerve function. This condition is called spinal stenosis. For women, there is evidence that menopause and related estrogen-loss are associated with lumbar disc degeneration, usually occurring during the first 15 years of the climacteric. The potential role of sex hormones in the etiology of degenerative skeletal disorders is being discussed for both genders.Mutations in several genes have been implicated in intervertebral disc degeneration. Probable candidate genes include type I collagen (sp1 site), type IX collagen, vitamin D receptor, aggrecan, asporin, MMP3, interleukin-1, and interleukin-6 polymorphisms. Mutation in genes – such as MMP2 and THBS2 – that encode for proteins and enzymes involved in the regulation of the extracellular matrix has been shown to contribute to lumbar disc herniation. Mechanisms
Degenerative discs typically show degenerative fibrocartilage and clusters of chondrocytes, suggestive of repair. Inflammation may or may not be present. Histologic examination of disc fragments resected for presumed DDD is routine to exclude malignancy.