This is a top view of a spinal disc (this particular one is a low back disc). Discs are composed of outer annular rings surrounding a jelly like center (nucleus pulposis). Discs attach the vertebrae together and at the same time allow for motion and shock absorption.
Spinal discs rely on the fact that we are up and about weight bearing for part of the day and then recumbent resting for a period of time. This up-down cycling creates a pumping mechanism which pulls oxygen and nutrients in and pushes waste products of cellular metabolism out. Motion is critical to disc health.
Relatively tiny tears may occur in the outer annular disc fibers and with time tears may increase in size center nucleus pulposis (think jelly) bulges its way outward into the tear. This may cause what is termed as a ‘herniation’, a ‘protrusion’, or if the bulge is around a lot of the disc, it is termed just a ‘bulge.’ Usually but not always the direction this occurs would be from the front toward the back or to the back and slightly left or right, of the body. Sometimes however, disc material herniates upward or downward directly into the vertebral body. This requires a breach in the integrity of the affected vertebral end plate.
A possible scenario would be that after years of stress, strain, aging, smoking, poor posture, accidents, lack of sleep, an individual simply bends and twists and SNAP: Disc tears. A particular episode may be neither felt nor heard in the moment, or ever, or it may swell and inflame with symptoms.
With injury normal disc pumping mechanisms are altered, reducing the exchange of oxygen and nutrition to the cells, thereby accelerating cellular aging. Eventually degenerative changes may become visualizable on x-rays such as degenerative disc disease (DDD) and/or facet degenerative joint disease (DJD). Generalized disc flattening (pancake disc) would eventually not be a surprising finding.
DDD may be termed mild, moderate, or severe and can occur at more than one spinal level. DDD doesn’t occur at all spinal levels equally because it is not the result of ‘normal aging’, but rather a response to prior specific damage.
Just below and to either side of the disc are a left and right spinal nerve ‘root’ (yellow in this illustration). Notice how close the outer edge of this particular spinal disc (gray rim) is to spinal nerve root. This could be problematic if the disc should tear and bulge or herniate outward toward either or both of these nerve roots. Nerves then pass through ‘foramen’ (holes) where disc material as well as bone (arthritic spurs) can impinge nerve, and this is worsened by flat disc (which can be worsened by being overweight).
When lower back nerve roots are pinched or inflamed by injured discs, symptoms may include: Back pain, groin pain, hip pain, buttock pain, pain down the back of the thigh, pain behind the knee, leg pain, ankle pain or foot pain. Numbness or tingling may also be noticed. Sometimes symptoms radiate into sexual organs and sometimes bowel and/or bladder function is disturbed. With weakness, legs may fee as they are going to give away, toes may hang up on carpeting, and walking may be impeded. Surprisingly, quite commonly, despite a serious disc tear, bulge, or herniation, nothing is really felt at all.