The lumbar region of the spine, commonly known as the lower back, consists of five vertebrae labeled L1 through L5 and is situated between the thoracic, or chest, region of the spine and the sacrum.
The two lowest segments in the lumbar spine, L4-L5 and L5-S1, carry the most weight and experience maximum movement, making these segments prone to injury and pain.
The most common cause of lower back pain is a torn or pulled muscle. Pain from a pulled back muscle, also called a muscle strain, is acute and often remains localized to the lower back area. A muscle strain can be accompanied by muscle spasms, as the body tries to stabilize the injury.
Lower back pain can also occur due to problems affecting the lumbar spinal discs. The discs can herniate or degenerate, and if the disc material irritates a nearby spinal nerve root, it can cause lower back pain or radiating pain in the legs and feet. This type of pain is called radicular pain or sciatica and travels down the leg through the large sciatic nerve. If the disc material compresses a nerve root, symptoms of radiculopathy, such as numbness, tingling, and weakness may occur in the affected leg.
Another type of lower back pain is called vertebrogenic pain, which occurs when the vertebral endplate, situated between the vertebral body and the intervertebral disc, becomes damaged. This pain is felt as a persistent dull ache or burning pain deep in the lower back area. Vertebrogenic pain usually flares up while sitting, standing, and bending the spine forward. In some cases, the pain may spread into the tissues surrounding the spine and the buttocks.
Dysfunction of the sacroiliac joints is another cause of lower back pain. These joints connect the triangular-shaped sacrum to the hip on each side of the spine. The SI joints can become painful due to chronic trauma or an acute injury. SI joint pain is similar to sciatica and is typically felt in the lower back, buttock, and thigh, along with a feeling of weakness and instability during certain movements or activities.
Other causes of lower back pain are degenerative spinal conditions, which occur due to wear and tear or natural aging of the spine. A few of these conditions include lumbar spinal stenosis, lumbar osteoarthritis, and degenerative spondylolisthesis.
Rarely, certain low back conditions, such as a severely herniated disc, can compress the spinal cord or cauda equina, which is a medical emergency. Symptoms include numbness, loss of balance, lower extremity weakness, and loss of bowel and bladder control.
It is important to understand the underlying cause of lower back pain in order to effectively treat the symptoms.