Eighty percent of human beings experience 

lower  back pain at some time during their lifetimes. 

This statement probably does not fully reflect

 the greater number of people who have

backaches that do not prevent them from 

working or performing everyday activities 

but make their daily activities painful.

The spine is a mechanical structure that supports the individual from birth troughout her or his life. 

The spine is known as the vertebral column and 

is essentially a column of one functional unit 

upon another. 

These functional units, posioned one upon 

another and balanced upon the sacrum, 

keep the column erect and in perfect balance against gravity.

The lumbar spine contains usually five 

sometimes there is four or six vertebrae 

and forms a normal curve in the erect posture called lordosis. 

Between the vertebrae and the discs emerge 

the nerves that descend into the legs. 

Every pair of vertebrae of the spinal column 

is separated by a disc. 

The disc is a hydraulic system that keeps 

the vertebrae apart. 

It acts to cushion any balance or pressure and permits the functional unit 

to move in flexion to the front, extension to 

the back, and to the side (lateral flexion).

The disc is made of two separate parts: an outer layer that is termed the annulus fibrosus 

and a central core termed the nucleus pulposus.

A central core, a transparent jelly, contains 

88 percent water. No blood vessels or nerves 

penetrate the nucleus which is tightly bounded peripherally by fibrous tracts. 

An outer layer is made up of concentric fibres, which are made of tissue called collagen. 

These fibres are layered so that the first layer

 of fibres crosses in an oblique direction 

from one vertebra to the other. The next inner

 layer of fibres crosses from one vertebra 

to the other in the opposite direction, thus 

causing these fibres to criss-cross 

and intertwine. Each layer of fibres goes in 

an opposite direction. 

This arrangement gives strength to the disc annulus, yet permits the vertebrae 

to move in any direction. The fibers of 

the annulus can strech to a limited degree therefore, when the vertebrae are compressed together, the fibres stretch but do not tear. 

When the vertebrae bare on each other, 

the fibres can stretch enough to allow bending 

but do not tear. When the fibres are twisted 

the fibres become stretched beyond their

 limits and thus tear.

A nerve root emerges through the foramen 

of each functional unit. There is a nerve root emerging between each pair of lumbar vertebrae, that is: L1-2, L2-3, L3-4, L4-5 and L5-S1 

and several nerve roots emerge through the foramen of the sacrum. 

A small branch from each nerve root arches backward to the back muscles, to the joints, 

to the skin, and to the ligaments that carry sensation of the lower back control the back muscles.

As they emerge from the spinal canal through

 the intervertebral foramen, the nerve roots 

are contained with a dural sac. This dural 

sac is well supplied by nerves, making it

 sensitive. The dural sac is a site of pain when irritated, inflamed, or injured!

Back pain caused by bad posture.

Increasing the lumbosacral angle by changing 

the angle of the sacrum changes the curvature 

of the lumbar spine. In this drawing, the lordosis

 is increased, causing possibly lower backache. 

Bad sleeping habits, especially lying on a soft, sagging bed or sleeping on one's stomach, 

cause lower backache from exessive lordosis.

Faulty sitting positions may cause lower backache. A chair that causes or allows exessive lordosis 

is worse than useless. "Sway back" from 

pregnancy or high heels increases lordosis 

and can cause lower backache. Not all sway

 backs are painful. 

It is oly when lordosis is exessive, or 

accentuated, that pain may result. 

Once the body has bent forward 45 degrees

 from an erect posture, 

the lumbar spine no longer can bend. From 

there on the pelvis rotates to allow the body 

to bend farther down. In order to allow 

the pelvis to rotate, the muscles behind 

the thighs and in the buttocks also have to 

be flexible. If the long muscles behind the tingh, 

meaning the hamstring muscles are exessively tight, the pelvis is prevented from rotating 

long before it has accomplished its potential movement. The reminder of bending becomes 

imposed upon the lower back, the lumbar spine. 

As the lumbar spine can bend only 

approximately 8 to 10 degrees at each 

functional unit if the pelvis is stopped midway 

in forward rotation, each functional unit must

 then bend exessively. 

The tissues of the lower back now must exeed 

the 8 to 10 degrees of normal flexion. 

This results in the tissues becoming overstreched and causing lower back pain!

As regards lower back lordosis, abrupt lifting 

and with unbent knees causes lower back pain!

Should the muscles on only one side of the spine become irritated and cause a spasm,

 The spine becomes pulled to one side. This

 twisting of the spine to one side is known 

as acute scoliosis.

Lower back pain resulting from spinal column 

stress can occur from activities as innocuous 

as sneezing, stepping down steps that are not there, stepping into a hole, 

coming up unexpectedly under an overhead

 beam, and hitting your head, etc.

Such activities put mechanical stress upon

 the spine that at the instant of stress, 

may be in an awkward position, such as while bending, twisting, and arching. 

If repeated incidences of these occur, the back

 can be weakened and become more 

susceptible to subsequent minor injuries.

When these activities occur,the powerful 

muscles of back perform powerful contractions

in a very small distance. They literally jam the joints together; these joints have been specified 

as being sensitive, and thus inflamation results from this injury. Inflamation is merely 

the reaction of the abused tissues. When 

these tissues are irritated by inflamation

 the muscles around them immediately go 

into protective spasm.

Lower back pain with Leg pain: 

The Ruptured Disk

If the disk bulges, ruptures, slips, or herniates, whatever term is used, 

the nucleus either ruptures out of its annular container or pushes the remaining 

untorn annular fibers out into the spinal canal 

or into the intervertebral foramen. 

The nucleus is under a great deal of pressure, 

held between the opposing end plates of the vertebrae and surrounded by annular fibres. 

If the fibres tear, the pressure within the 

nucleus exerts force in an attempt to allow 

the nucleus to escape. It cannot escape 

through the end plates, so it forces its way outwards to the periphery.

A patient may have leg pain originating from

 the lumbar spine without back pain 

or may have both back pain and leg pain. 

Leg pain existing and originating from the back

is medically termed sciatica.

Sciatica, which is sciatic nerve pain, is 

considered to result from irritation 

or inflammation of the nerve roots. 

Nature always responds to a painful inflamed 

tissue and prevents it from being irritated. Therefore, the muscles of the legs will go into spasm to prevent the leg from becoming 

elevated, or bent at the hip. 

The back muscles will go into spasm to prevent 

the back bending, which also stretches the nerve.

The pain can be nagging, aching, stabbing, shooting, or a burning sensation felt in the leg

 in the distribution of the specific nerve root.

It is only when the herniating nucleus presses against the deep surface of the posterior longitudinal ligament that the nerve endings of the ligament are stretched causing lower back pain (lumbago). 

Finally compression of the nerve roots by the herniating disc causes nerve root pain, i.e. sciatica.