Learn about common causes of low back pain, including disc, facet joint, and sacroiliac joint problems, and when to seek specialist assessment for persistent symptoms.
Summary:
Low back pain is extremely common, and in most cases there is no single clear cause. When a structural cause can be identified, the pain often comes from the intervertebral disc, the lumbar facet joints, or the sacroiliac joint. If back pain persists, early assessment by a pain specialist or spine specialist can help identify the cause and guide treatment.
Low back pain refers to pain felt between the lower ribs and the buttocks. It is one of the most common health problems worldwide. At any given time, around 7 to 8 out of every 100 people are affected by low back pain. Its causes are often complex. In many people, no single structure can be clearly blamed. In others, the pain may be linked to a specific part of the spine. Occasionally, low back pain may also be related to another underlying illness.
Most cases are classified as non-specific low back pain, which means no single definite cause can be identified. The other group is structural low back pain, where clinical examination, imaging, or targeted diagnostic procedures suggest a more specific pain source. The most common structural causes include discogenic low back pain, lumbar facet joint pain, and sacroiliac joint pain.
Discogenic pain
Intervertebral discs sit between the vertebrae and act like shock absorbers, helping the spine absorb load during everyday movement. As people get older, discs gradually lose water content and become more degenerated. On MRI scans, a degenerated disc may appear darker than a healthy one, although this does not always mean it is the true source of pain.
When the disc itself becomes painful, patients often describe a deep, central ache or dull pain in the lower back, and the exact spot may be hard to pinpoint. The pain is often worse with sitting, bending forwards, lifting, coughing, or sneezing because these activities increase pressure inside the disc. Many people feel better when lying flat. This type of pain does not always come with a slipped disc or nerve compression.
Facet joint pain
At the back of each lumbar vertebra is a pair of small joints called facet joints. These are synovial joints, similar in basic structure to the knee, and they help guide spinal movement through small, controlled motions. They can become painful because of long-term wear and tear, irritation, or inflammation.
Facet joint pain is usually felt on one side of the lower back, and patients can often point quite clearly to where it hurts. It tends to be worse when leaning backwards, twisting, or standing for a long time, and it may ease when bending forwards. Morning stiffness is also common, especially after rest or prolonged sitting.
Sacroiliac joint pain
The sacroiliac joints lie between the sacrum, at the base of the spine, and the pelvis. Their job is to transfer weight from the upper body to the legs. Pain can arise when the joint is irritated, inflamed, injured, or affected by pelvic changes during or after pregnancy.
Patients usually feel marked aching pain in one buttock. Sometimes the pain spreads into the back of the thigh or the groin. It is often particularly painful when standing on one leg, climbing stairs, turning in bed, or standing up after sitting for a long time.
Serious causes
Although most low back pain is related to benign degeneration or mechanical strain, a small number of cases are caused by more serious conditions. These include fractures, bacterial infection, autoimmune disease, or cancer that has spread to the spine. Severe degeneration can also lead to nerve compression, which may cause lasting damage if not treated in time.
Seek medical attention promptly if low back pain is associated with any of the following warning signs:
– Pain that continues at night or wakes you from sleep.
– Fever or unexplained weight loss.
– Leg weakness, numbness, or loss of bladder or bowel control.
If low back pain lasts for more than a few weeks, keeps coming back, or starts to interfere with daily life, it is worth seeking medical assessment early. A careful diagnosis can help identify the cause and lead to more targeted treatment.
Information provided by Dr. Lee Yuk-ming, Specialist in Pain Medicine
