Causes of lower back pain
Back pain is a symptom. Most back pain is musculo-skeletal in origin. Pain arising from other organs may be felt in the back. This is called referred pain. Many intra- abdominal disorders - such as appendicitis, aneurysms, kidney diseases, bladder infections, pelvic infections and ovarian disorders, amongst others - can cause pain referred to the back. Your doctor will consider this when evaluating your pain.
- Musculo-skeletal lower back pain is the most common cause of back pain. It is commonly caused by poor posture, twisting awkwardly, or incorrect lifting techniques.
- Nerve root syndromes are those that produce symptoms of nerve impingement (a nerve is touched), often due to a herniation (or bulging) of the disc between the lower back bones. Sciatica is an example of nerve root impingement. Impingement pain tends to be sharp, in one spot (or can radiate to other parts of the body as in the case of sciatica where pain may be felt down the leg) and associated with numbness in the area of the leg that the affected nerve supplies.
- Herniated, or slipped, discs are produced as the spinal discs degenerate or grow thinner. The jelly-like central portion of the disc bulges out of the central cavity and pushes against a nerve root. Intervertebral discs begin to degenerate by the third decade of life. Slipped discs are found in one-third of adults older than 20. However only 3% of these produce symptoms of nerve impingement.
- Spinal stenosis is an abnormal narrowing of the spinal canal. It can occur as intervertebral discs lose moisture and volume with age, which decreases the canal space. This, coupled with disease in joints of the lower back, causes spinal canal narrowing. These changes in the disc and the joints produce symptoms and can be seen on an X-ray or scans. A person with spinal degeneration may have morning stiffness or pain while standing for a long time or walking even short distances. Even minor trauma under these circumstances can cause inflammation and nerve root impingement, which can produce classic sciatica without disc rupture or herniation.
- Cauda equina syndrome is a medical emergency. Disc material expands into the spinal canal, which compresses the nerves. A person experiences pain, possible loss of sensation and bowel or bladder dysfunction. This can include inability to control urination, causing incontinence, or the inability to begin urination.
- Musculoskeletal pain syndromes that produce lower back pain include myofascial pain syndromes and fibromyalgia.
- Myofascial pain is characterised by pain and tenderness over localised areas (trigger points), loss of range of motion in the involved muscle groups and pain radiating in a characteristic distribution but restricted to a peripheral nerve. Relief of pain is often reported when the involved muscle group is stretched.
- Fibromyalgia is a poorly understood condition defined as causing pain and tenderness at 11 of 18 ‘tender points’ when touched, one of which is the lower back area. Generalised stiffness, fatigue and muscle ache are reported.
- Other skeletal causes of lower back pain include osteomyelitis, sacroiliitis, and osteoporosis vertebral fractures. This pain is often worse at night and when sitting or standing for a long time.
- Tumours, possibly cancerous, can be a source of skeletal pain in the back.