The lumbar spine contains 5 moderately large vertebrae which sit atop the sacrum. These bony segments act as attachments for muscles and ligaments in the lumbar spine and also encase and protect the lower spinal cord and lumbar nerve roots.
Because the lumbar vertebrae are located between the pelvis and upper torso, the degree of stresses endured by the lumbar spine are great. These abnormally high degrees of stress result in frequent lumbar vertebral subluxations - misalignments and improper motion patterns of the lumbar vertebrae. If left uncorrected, these misalignments and faulty biomechanics of the lower spine can result in spinal injury and irreversible degenerative changes.
The lumbar discs connect adjacent lumbar vertebrae to one another and cushion the spine as well as permit motion between the individual vertebrae. As stated above, the lumbar spine is a "transitional" area between the pelvis and upper torso, thus, resulting in high degrees of spinal stress. This results in the 4th and 5th lumbar discs suffering more injuries than all other spinal discs combined.
Disc herniations in the lumbar spine are the most common causes of "sciatica", meaning pain running down the back of the leg in the area of the sciatic nerve. Possible symptoms include pain, numbness, tingling or weakness in the legs and/or feet.
In rare cases, a lumbar disc herniation can compress the spinal nerves which provide motor control to the bowel and bladder. Although rare, if you're having back pain and experience a loss of bowel and/or bladder control, immediate medical intervention is required. Without immediate decompression the loss may become permanent.
The facet joints in the lumbar spine allow for considerable amounts of flexion but a much lesser degree of extension and rotation. These joints must withstand large amounts of stress from the body and as a result are prone to acute and repetitive injuries and degenerative arthritis.
Facet joints are most commonly injured during movements involving a rotational or twisting component. When injured, pain is often sharp and localized to the area of the affected facet joint. Later in life, if spinal problems have been allowed to linger without appropriate rehabilitation, arthritis will likely be present. If severe enough, as is commonly the case, bony arthritic enlargement of the joint can impinge upon spinal nerve roots and produce symptoms pain, numbness, and tingling down the leg, as well as leg weakness, in addition to back pain.
The lumbar spinal nerve roots exit openings formed between adjacent lumbar vertebrae termed the intervertebral foramina or IVF. The weakest aspect of the spinal disc is unfortunately in close proximity to the IVF. Thus, disc injuries commonly result in discal materials compressing, stretching or irritating the nerve roots exiting the IVF's.
Because the nerve roots exiting the lumbar spine innervate structures in the lower extremities, any compression, stretching or other irritation will result in numbness, tingling, pain or weakness in the leg(s) and/or feet. This may result from vertebral malpositions, disc herniations, arthritic changes to the vertebrae and facet joints, or even abnormalities within the muscles (piriformis syndrome).
The paraspinal muscles in the lumbar spine attach to the spinal vertebrae and pelvis to provide the torso with movement. These muscles must be strong to control the upper torso about the pelvis and thus are frequently overworked and injured. The pain associated with paraspinal muscle injury is generally a dull, boring, generalized ache in the area of the lower back.
The sacroiliac joints are located between the sacrum and the ilium bones of the pelvis. These joints may also become irritated or injured resulting in lower back pain, buttock pain, and occasionally leg pain.
This condition tends to be more common in women, especially during pregnancy when hormonal changes and pressure from the forming fetus increase the stress on these joints.