Lumbar intervertebral disc degeneration in low back pain.

Intervertebral disc degeneration is characterized by deterioration in structural support that is potentially followed by stimulated neuronal ingrowth, and dysfunction of cellular physiology in the disc. Discogenic low back pain originates from nociceptors within the intervertebral disc or the cartilage endplate. This narrative review examines the mechanisms of disc degeneration, the association between degeneration and pain, and the current diagnosis and treatment of discogenic low back pain. Mechanisms of disc degeneration include dysregulated homeostasis of the extracellular matrix of the disc, altered spine mechanics, DNA damage, oxidative stress, perturbed cell signaling pathways, and cellular senescence. Although disc degeneration is more common in individuals with low back pain than in asymptomatic ones, degeneration occurs in a large proportion of asymptomatic individuals. Therefore, degeneration itself is not sufficient to trigger low back pain. Imaging and discography are common diagnostic tools of discogenic low back pain but have limited validity to diagnose discogenic pain. Most of current treatments options are not specific to discogenic pain but are unspecific treatments of low back pain of any origin. There is an urgent need to clarify and distinguish the molecular mechanisms of discogenic pain from mechanisms of disc degeneration that are not involved in nociception. Future research should make use of current methods to study molecular mechanisms of human pain in comprehensively and quantitatively phenotyped patients with low back pain, with the objective to identify molecular triggers of discogenic pain and determine the relationship between molecular mechanisms, pain, and patient-relevant outcomes.