The Lumbar spine
The low back supports the weight of the upper body and provides mobility for everyday motions such as bending and twisting. Muscles in the low back are responsible for flexing and rotating the hips while walking, as well as supporting the spinal column. Nerves in the low back supply sensation and power the muscles in the pelvis, legs, and feet.
Most acute low back pain results from injury to the muscles, ligaments, joints, or discs. The body also reacts to injury by mobilizing an inflammatory healing response. While inflammation sounds minor, it can cause severe pain.
There is a significant overlap of nerve supply to many of the discs, muscles, ligaments, and other spinal structures, and it can be difficult for the brain to accurately sense which is the cause of the pain. For example, a degenerated or torn lumbar disc can feel the same as a pulled muscle – both creating inflammation and painful muscle spasm in the same area. Muscles and ligaments heal rapidly, while a torn disc may or may not.
Lower Back Pain Symptoms
Low back pain can incorporate a wide variety of symptoms. It can be mild and merely annoying or it can be severe and debilitating. Low back pain may start suddenly, or it could start slowly—possibly coming and going—and gradually get worse over time.
Depending on the underlying cause of the pain, symptoms can be experienced in a variety of ways. For example:
Pain that is dull or achy, contained to the low back
Stinging, burning pain that moves from the low back to the backs of the thighs, sometimes into the lower legs or feet; can include numbness or tingling (sciatica)
Muscle spasms and tightness in the low back, pelvis, and hips
Pain that worsens after prolonged sitting or standing
Difficulty standing up straight, walking, or going from standing to sitting
In addition, symptoms of lower back pain are usually described by type of onset and duration:
Acute pain. This type of pain typically comes on suddenly and lasts for a few days or weeks, and is considered a normal response of the body to injury or tissue damage. The pain gradually subsides as the body heals.
Subacute low back pain. Lasting between 6 weeks and 3 months, this type of pain is usually mechanical in nature (such as a muscle strain or joint pain) but is prolonged. At this point, a medical workup may be considered, and is advisable if the pain is severe and limits one’s ability to participate in activities of daily living, sleeping, and working.
Chronic back pain. Usually defined as lower back pain that lasts over 3 months, this type of pain is usually severe, does not respond to initial treatments, and requires a thorough medical workup to determine the exact source of the pain.
Types of Low Back Pain
There are many ways to categorize low back pain – two common types include:
Mechanical pain. By far the most common cause of lower back pain, mechanical pain (axial pain) is pain primarily from the muscles, ligaments, joints (facet joints, sacroiliac joints), or bones in and around the spine. This type of pain tends to be localized to the lower back, buttocks, and sometimes the top of the legs. It is usually influenced by loading the spine and may feel different based on motion (forward/backward/twisting), activity, standing, sitting, or resting.
Radicular pain. This type of pain can occur if a spinal nerve root becomes impinged or inflamed. Radicular pain may follow a nerve root pattern or dermatome down into the buttock and/or leg. Its specific sensation is sharp, electric, burning-type pain and can be associated with numbness or weakness (sciatica). It is typically felt on only one side of the body.
Causes of lower back pain
Lower back pain is often caused by a torn or pulled muscle or ligament. This can occur after lifting a heavy object, a sudden movement, poor back posture, or a sports injury. A low back sprain or strain can happen suddenly, or can develop slowly over time from repetitive movements. While sprains and strains do not sound serious and do not typically cause long-lasting pain, the acute pain can be severe.
Muscle Strain and Ligament Sprain
A low back sprain or strain can happen suddenly, or can develop slowly over time from repetitive movements.
Strains occur when a muscle is stretched too far and tears, damaging the muscle itself.
Sprains happen when over-stretching and tearing affects ligaments, which connect the bones together.
For practical purposes, it does not matter whether the muscle or ligament is damaged, as the symptoms and treatment are the same.
Common causes of sprain and strain include:
Lifting a heavy object, or twisting the spine while lifting
Sudden movements that place too much stress on the low back, such as a fall
Poor posture over time
Sports injuries, especially in sports that involve twisting or large forces of impact
While sprains and strains do not sound serious and do not typically cause long-lasting pain, the acute pain can be quite severe.