What is the lumbar spine?
The lumbar spine is the part of the spine between the thoracic spine and the sacrum. It usually consists of five vertebrae, L1 to L5. The vertebrae are larger than those higher up in the spine because they have to carry more weight.
Between the vertebrae are discs, and at the back are facet joints. Ligaments and deep back muscles stabilize the area. Nerve roots leave the spinal canal and continue towards the pelvis, buttocks and legs.
Low back pain is very common. It can be localized or radiate to the buttocks and legs. A clear pattern of pain, sensory involvement, and weakness can provide clues as to whether nerve roots are involved.
What is the function of the lumbar spine?
The lumbar spine primarily allows for flexion and extension, but also some lateral bending and rotation. It transfers forces between the upper body and the pelvis and needs to be stabilized by the abdominal muscles, back muscles, pelvic floor, and hips.
The discs distribute pressure between the vertebrae while the facet joints control movement. The nerves in the area affect sensation and muscle strength in parts of the legs. Therefore, a change in the lumbar spine can cause both back pain and symptoms further down.
Strength, range of motion and gradual loading are important for function. A single posture is rarely the entire explanation for long-term problems.
The load on the lower back varies with pace, technique, fatigue and how often the same movement is repeated. The body is adaptable, and gradually increasing activity is usually better than prolonged rest for uncomplicated problems.
Common lower back problems
Common low back pain can come from discs, facet joints, muscles and ligaments without an exact structure being able to be pinpointed. The discomfort can occur after strain or come on gradually. Read more about low back pain.
A herniated disc can irritate or press on a nerve root and cause sciatica with radiating pain, numbness or weakness in the leg. Spinal stenosis means that the space for the nerves has become narrower and can cause pain or a feeling of heaviness when walking.
Other causes include fracture, inflammation, infection, or disease of organs near the back. These are less common but important to consider if you have warning symptoms.
When should you seek care for your lower back?
Contact healthcare if the pain is severe, lasts a long time, recurs frequently or is combined with a clear radiation, numbness or weakness. Assessment is also needed in the event of fever, night pain, unexplained weight loss, previous cancer or after major trauma.
Seek emergency care if you have difficulty urinating, cannot feel when your bladder is full, lose control of urine or stool, experience numbness in your lower abdomen, or rapidly increasing weakness in your legs. These may be signs of serious nerve damage.
Sudden severe back pain along with abdominal pain, feeling faint or having a poor general condition should also be assessed immediately.
How are low back problems investigated?
The doctor will ask about the course of the pain, its radiating characteristics, and how it affects function. The examination may include gait, mobility, reflexes, muscle strength, sensation, and nerve stretching tests.
Imaging is not routinely needed for short-term, uncomplicated low back pain. X-rays can show the skeleton and some age-related changes. CT may be relevant for fractures or detailed skeletal assessment. MRI is primarily used when nerves, discs, spinal canal, inflammation, tumor, or infection need to be assessed.
Blood tests and other examinations may be needed if the symptoms suggest inflammation, infection, or an organ-related cause.
When can MRI of the lumbar spine be relevant?
MRI of the lumbar spine may be relevant for long-term or increasing symptoms with nerve involvement, prior to certain treatments, or when more serious causes need to be ruled out. MRI can show herniated discs, spinal stenosis, nerve roots, bone marrow, and soft tissues.
A normal finding on MRI does not necessarily mean that the pain is the cause. Disc changes also occur in people without symptoms. Therefore, the images should always be linked to a neurological examination and the pattern of the symptoms.
In acute trauma, CT or X-ray may be better for the skeleton. In uncomplicated back pain, clinical assessment and gradual activity are often more important than early imaging.
Limitations and next steps
Low back pain often improves without surgery. Treatment may include information, adapted activity, physiotherapy, pain relief and treatment of the underlying disease. Imaging findings alone do not determine treatment.
If the MRI shows nerve damage or other changes, the next step may be follow-up, specialist assessment, injection treatment or surgery, but the decision depends on symptoms, function and how the problems develop.
In chronic pain, sleep, stress, fear of movement, and reduced physical capacity can also affect recovery. This does not mean that the pain is imaginary, but that the nervous system and tissues need to be assessed as a whole. A plan with realistic activity goals may be more important than trying to find perfect posture.