Lower back pain is the single most common musculoskeletal complaint worldwide, affecting roughly 629 million people in 2021 alone. Most cases trace back to strained muscles or ligaments, but the full list of causes ranges from bulging discs and narrowed spinal canals to inflammatory diseases and even your own pain-related beliefs. Understanding what’s behind your pain is the first step toward getting it to stop.
Muscle and Ligament Strains
Strains and sprains are the most common cause of lower back pain. A strain means you’ve overstretched or torn a muscle or tendon; a sprain means the same thing happened to a ligament. The trigger is often obvious: lifting something too heavy, twisting awkwardly, or using poor form during exercise. But sometimes the trigger is surprisingly minor. Sneezing, coughing, or simply bending over to pick something up can strain the lower back if the tissues are already fatigued or tight.
These injuries typically heal within a few days to a few weeks because muscles and ligaments have a decent blood supply. The pain tends to be localized to one area of the lower back, feels worse with movement, and improves with rest. If your pain started suddenly after a specific activity and stays in the back without shooting down your leg, a strain or sprain is the most likely explanation.
Disc Problems
Each spinal disc has a soft, gel-like center surrounded by a tougher outer ring. A herniated disc happens when part of that soft center pushes through a tear in the outer ring. This doesn’t always cause pain on its own. Symptoms show up when the bulging material presses on a nearby nerve root, which can send sharp or burning pain down into the buttock and leg (often called sciatica).
Disc herniations in the lower back are most common between the ages of 30 and 50, when the discs still have enough gel-like material to herniate. The pain is often worse when you sit, bend forward, or bear down (like during a cough or sneeze), because those positions increase pressure on the disc. Many herniated discs improve over several weeks without surgery as the body gradually absorbs the protruding material and inflammation settles.
Facet Joint Wear and Tear
Behind each spinal disc, a pair of small joints called facet joints connect one vertebra to the next. These joints let you twist and bend. Like any joint, they develop arthritis over time, and the cartilage lining them wears down. Facet joint problems account for an estimated 15% to 40% of chronic lower back pain cases.
Facet-related pain typically feels like a deep ache on one or both sides of the spine. It tends to get worse when you arch your back, stand for long periods, or get out of bed in the morning. Unlike disc herniations, facet joint pain usually stays in the back rather than radiating down the leg, though it can refer pain into the buttocks or upper thighs.
Spinal Stenosis
Spinal stenosis means the channel that houses the spinal cord and nerves has narrowed. In the lower back, this is almost always a gradual process driven by arthritis, thickened ligaments, and bulging discs that slowly encroach on the available space. It’s most common after age 50.
The hallmark symptom is pain or heaviness in the legs that gets worse with walking or standing upright and improves when you sit down or lean forward. Many people notice they can walk longer in a grocery store while leaning on a cart than they can on a flat sidewalk. That’s because leaning forward opens up the spinal canal slightly and takes pressure off the nerves. The pain often affects both legs and can include numbness, tingling, or a feeling of weakness.
Inflammatory Back Pain
Not all lower back pain comes from wear, tear, or injury. A group of conditions called axial spondyloarthritis involves the immune system attacking the joints where the spine meets the pelvis. This type of back pain typically appears before age 45, with a peak onset between 20 and 30 years old.
The pattern is distinctive: stiffness that lasts more than 30 minutes every morning, pain that improves with movement rather than rest, and symptoms that develop gradually over weeks or months rather than after a single event. The most well-known form, ankylosing spondylitis, has a strong genetic component. Roughly 85% to 95% of white patients with the condition carry a specific genetic marker called HLA-B27. If your back pain wakes you in the second half of the night and loosens up once you start moving, inflammatory back disease is worth investigating.
How Body Weight and Sitting Interact
Carrying extra weight puts additional mechanical load on the lower spine with every step, and the data backs this up clearly. People who are overweight have about a 41% higher risk of chronic lower back pain compared to those at a normal weight, and people with obesity face a 48% higher risk.
Sitting time alone doesn’t appear to be an independent risk factor, which may surprise anyone who blames their desk chair. But the combination matters. In people with a BMI of 30 or higher, sitting more than 4.5 hours per day significantly amplifies the risk of chronic pain. In other words, excess weight loads the spine, and prolonged sitting removes the muscular activity that would otherwise help support it. If you carry extra weight and spend most of your day seated, those two factors are working together against your lower back.
When Pain Becomes Chronic: The Role of Your Brain
About 1 in 5 people with acute lower back pain go on to develop chronic symptoms lasting three months or longer. The transition isn’t purely physical. Prospective research tracking people from their first episode of back pain found that baseline pain severity and negative expectations about recovery were among the strongest predictors of who still had pain at three months. Fear of movement also played a role in the shift from short-term to long-term pain.
This isn’t the same as saying the pain is “in your head.” What happens is that the nervous system becomes more sensitive over time, amplifying pain signals even after the original tissue injury has healed. Believing that your back is fragile, avoiding all movement out of fear, or expecting the worst outcome can reinforce that sensitization. Addressing those beliefs early, through gradual return to activity and education about what’s actually happening in the spine, reduces the chance of pain becoming a permanent fixture.
Fractures
The bones of the lower spine can fracture from high-energy trauma like a car accident or a fall from height. But in older adults, especially those with osteoporosis, a vertebra can crack under forces as minor as bending to tie a shoe. These compression fractures cause sudden, localized pain that’s often worst when standing or walking and eases when lying down. They’re a common and underdiagnosed cause of back pain in people over 60.
Red Flags That Need Immediate Attention
A rare but serious cause of lower back pain is cauda equina syndrome, where the bundle of nerves at the base of the spine becomes severely compressed. The most telling symptom is urinary retention: your bladder fills, but you don’t feel the normal urge to go. Other warning signs include loss of bowel or bladder control, numbness in the groin or inner thighs (sometimes called “saddle anesthesia”), sudden weakness in one or both legs, and new sexual dysfunction. This is a surgical emergency. Permanent nerve damage can result if the pressure isn’t relieved within hours.
Other patterns worth getting checked promptly include back pain accompanied by unexplained weight loss, pain that wakes you from sleep and doesn’t respond to position changes, fever alongside back pain, or a history of cancer. These don’t necessarily mean something dangerous is happening, but they warrant imaging and evaluation rather than a wait-and-see approach.