The most common reason your lower back hurts is a muscle strain or ligament sprain, often from lifting something awkwardly, twisting suddenly, or simply sitting too long in one position. These soft-tissue injuries account for more cases of low back pain than any other cause. The reassuring news: roughly 90% of low back pain episodes improve without surgery, and most resolve within four to six weeks with basic self-care.
That said, “why does my lower back hurt?” has many possible answers. Your lumbar spine is a complex structure of five large vertebrae, five cushioning discs, ten branching nerves, and layers of muscles and ligaments that all work together to support your upper body. A problem with any of these structures, or even with organs nearby, can register as lower back pain.
Muscle Strains and Sprains
A strain means you’ve overstretched or torn muscle fibers. A sprain means the same thing happened to a ligament. Both feel similar: a dull ache or sharp pain in the lower back that gets worse with movement, especially bending or twisting. Common triggers include picking up a heavy box with a rounded back, a sudden sports movement, or even a hard sneeze when your core is off guard.
These injuries typically heal on their own. The American College of Physicians recommends starting with non-drug treatments like superficial heat (a heating pad or warm bath), massage, acupuncture, or spinal manipulation. If you want medication, over-the-counter anti-inflammatory painkillers are the first-line option. Most people feel significantly better within a few weeks, though mild stiffness can linger a bit longer.
Disc Problems
Between each pair of vertebrae sits a rubbery disc that absorbs shock. Over time, or after an injury, a disc can bulge, tear, or leak its gel-like center outward. This is a herniated disc. When the bulging material presses on one of the spinal nerves branching off the lumbar spine, you can feel pain, tingling, or numbness that travels down into your leg or foot.
A related issue is degenerative disc disease, where discs gradually lose height and hydration with age. As the space between vertebrae shrinks, nerves can get pinched. This doesn’t always cause symptoms, but when it does, the pain tends to be a chronic, low-grade ache that flares with prolonged sitting or bending forward.
Sciatica and Nerve Compression
If your lower back pain shoots down one leg, possibly reaching your calf or foot, you’re likely dealing with sciatica (also called lumbar radiculopathy). The sciatic nerve is the longest nerve in your body, and it branches off the lower lumbar spine. A herniated disc, bone spur, or narrowing of the spinal canal can compress it.
Spinal stenosis is one common cause of nerve compression, especially after age 50. The bony canal that houses your spinal cord gradually narrows, squeezing the nerves. People with stenosis often notice that walking or standing makes the pain worse, while sitting or leaning forward brings relief, because leaning opens up a bit of space in the canal.
Lifestyle Factors That Contribute
Prolonged sitting is one of the most underappreciated contributors. Research on university employees found that people who sat more than 10 hours a day were 74% more likely to experience back pain than those who sat less, even after adjusting for age, gender, and occupation. You don’t need to quit your desk job, but breaking up long stretches of sitting with short walks or standing breaks makes a measurable difference.
Weak core muscles are another major factor. Your abdominal and back muscles work as a team to stabilize your spine. When they’re deconditioned, your lumbar discs and joints absorb forces they weren’t designed to handle alone. Regular core-strengthening exercises (planks, bird-dogs, side bridges) help distribute load more evenly across the spine. Even 10 to 15 minutes a day can reduce flare-ups over time.
Excess body weight, poor sleep posture, and repetitive bending or lifting at work all compound the problem. Each one adds a little more mechanical stress to a region of the spine that already bears the majority of your upper body’s weight.
When Pain Comes From Somewhere Else
Not all lower back pain originates in the spine. Kidney stones and kidney infections commonly present as pain in the lower back or flank, often accompanied by fever, painful urination, or blood in the urine. Colon problems can also refer pain to the lower back. In women, endometriosis and ovarian cysts sometimes cause deep, aching low back pain that worsens around menstruation.
If your back pain doesn’t change with movement or position, and especially if it comes with other symptoms like fever, nausea, or changes in urination, the source may be an internal organ rather than a spinal structure.
The Role of Stress and Mental Health
Chronic back pain isn’t purely mechanical. Pain science has moved toward a model that acknowledges both physical and psychological factors. Stress, anxiety, and a thinking pattern called catastrophizing (expecting the worst possible outcome from pain) can amplify how intensely you feel back pain and how long it lasts. Studies show that successful recovery from back pain, even after physical treatments like exercise or manual therapy, is often driven by changes in psychological factors like fear avoidance and pain self-efficacy, meaning your confidence that you can function despite the pain.
This doesn’t mean the pain is “in your head.” It means your nervous system processes pain signals through emotional filters, and addressing those filters with cognitive behavioral therapy or stress management techniques can produce real, measurable improvements in pain levels.
When Imaging Is Actually Needed
Most people with lower back pain do not need an MRI or CT scan. According to the American College of Radiology, uncomplicated acute back pain is a self-limiting condition that doesn’t warrant imaging. Scans are recommended only after four to six weeks of conservative treatment that hasn’t helped, or when specific red flags are present.
Those red flags include:
- Loss of bladder or bowel control
- Numbness in the groin or inner thighs (saddle anesthesia)
- Progressive weakness in both legs
- Unexplained weight loss
- History of cancer, IV drug use, or prolonged steroid use
- Pain following significant trauma, or a minor fall in someone with osteoporosis
The combination of new urinary symptoms with back pain or sciatica is particularly important. This pattern can indicate cauda equina syndrome, a rare but serious condition where the bundle of nerves at the base of your spinal cord is compressed. It requires urgent MRI and, if confirmed, emergency treatment to prevent permanent damage.
What Recovery Looks Like
For the vast majority of lower back pain episodes, the path forward is straightforward: stay as active as you comfortably can, use heat and gentle movement to manage symptoms, and avoid prolonged bed rest, which actually slows recovery. Physicians generally recommend four to six weeks of conservative care before considering more invasive options.
Pain that persists beyond 12 weeks is classified as chronic. About 23% of adults worldwide live with chronic lower back pain, so if yours isn’t resolving on the expected timeline, you’re far from alone. At that point, a combined approach tends to work best: targeted exercise, manual therapy, and attention to the psychological factors that keep pain signals elevated. Building strength, staying active, and managing stress aren’t just nice ideas. For most people with lower back pain, they’re the most effective treatment available.