Herniated (slipped) disc happens when all or only a portion of an intervertebral disc is forced through the weak part of the disc thus exerting pressure to the adjacent nerves or spinal cord. Intrinsic degeneration of the intervertebral disc or extrinsic compression of the neural structures in the spinal canal can cause radicular pain. The loss of disc height, which can alter the mechanics of the axial skeleton, may result to disc degeneration. The said changes might produce in other structures such as the zygapophyseal (facet) joints and may result to spinal stenosis. Radicular pain is defined as pain radiating in the distribution of spinal nerve caused by the irritation of the dorsal root ganglion while discogenic pain is an axial pain originating in a degenerative disc.    
Considred to be a critical part of the load-bearing structures of the spinal column, the structural component of the invertebral disc make it capable of changing shape and absorbing shock thus allowing movement. The dysfunction of the intervertebral disc is brought about by multiple factors namely trauma, aging or the degenerative disorders of the spine.  The boundary between nucleus and annulus become less evident as a person ages, furthermore as a person grow older the nucleus of the intervertebral disc becomes less gel-like and more fibrotic. Trauma results from activities such as slipping, lifiting while in a flexed position, suppressing a sneeze or falling on the buttocks. Degeneration like in osteoarthritis or ankylosing spondylitis predisposes the misalignment of the vertebral column of the client. 
A research on the mechanism of intervertebral disc pointed out several pathophysiologic processes. It includes the changes that occur in aging, loss of proteoglycan which is mentioned as the most significant biochemical change that occurs in disc degeneration. It is inferred that the loss of proteoglycan leads to loss of hydration. Another mechanism is the loss of collagen fiber. Unlike with the proteoglycan, the loss of collagen is not that evident. Furthermore, it is deduced that the biochemistry of disc degeneration do not just include increase fragmentation of collagen and proteoglycans but also it includes the increase fragmentation of fibronectin populations. The said mechanisms contribute to the functional changes of the intervertebral disc. 
The cervical and lumbar portion of the vertebrae is commonly affected by the dysfunction because it is the most flexible areas of the spine where bending of the vertebral column and support of the mass are greatest. Around 90 to 95% of herniations in the lumbar vertebrae occur in L5 or L% to S1 regions respectively. With regards to the herniation at the cervical spine, the most often affected portion is C1 to C7 and C6 to C6. The protrusion usually happens posteriorly toward the intervertebral foramen where the annulus fibrosus is thin and poorly supported by the anterior or posterior ligaments....