Lower back pain is most often caused by a muscle strain, ligament sprain, or irritation of the structures around your lumbar spine. About 13% of U.S. adults deal with chronic low back pain, making it one of the most common reasons people miss work or visit a doctor. The good news is that the vast majority of cases resolve on their own within a few weeks, and the cause is usually mechanical, meaning something in your muscles, joints, or discs rather than a serious underlying disease.
That said, “lower back pain” is a broad symptom with a wide range of possible explanations. Understanding what yours feels like, where it radiates, and how long it’s lasted can help you figure out what’s going on and whether you need professional help.
Muscle Strains and Ligament Sprains
The most common culprit behind sudden lower back pain is a strain or sprain. These sound similar but involve different tissues. A strain is an injury to a muscle or tendon (the tough bands connecting muscle to bone). A sprain is the stretching or tearing of a ligament (the bands connecting bones to each other at a joint). Both happen when you twist, pull, or overload your lower back, whether from lifting something heavy, moving awkwardly, or even sleeping in an odd position.
Strain and sprain pain tends to feel like a deep ache or stiffness centered in the lower back. It often gets worse with movement and improves with rest. You might notice muscle spasms or tightness on one side. This type of pain typically peaks within the first 48 hours and gradually improves over two to six weeks.
Herniated Discs and Nerve Compression
Between each vertebra in your spine sits a rubbery disc that acts as a shock absorber. When the soft inner material of a disc pushes through a crack in its tougher exterior, that’s a herniated disc. Most herniated discs happen in the lower back, and they don’t always cause symptoms. You can have one and never know it.
When a herniated disc does press on a nearby nerve, the symptoms go beyond simple back pain. You’ll typically feel pain in your lower back, buttocks, thigh, and calf, sometimes reaching into your foot. The pain often affects one side of the body. Coughing, sneezing, or bending can send a sharp jolt down your leg. You may notice numbness, tingling, or weakness in the affected leg, and the muscles served by the compressed nerve can weaken enough to make you stumble or have trouble lifting objects.
Sciatica: Pain That Travels Down Your Leg
If your lower back pain shoots into your buttock and down the back of one leg, you’re likely dealing with sciatica. The sciatic nerve is the largest nerve in your body, running from your lower spine through your pelvis, down the back of your thigh, and all the way to your heel. When something compresses or irritates this nerve (a herniated disc, bone spur, or tight muscle), the result is pain that follows its path.
Sciatica typically causes mid-buttock pain that radiates down one leg. It can feel like burning, tingling, or an electric shock. Sitting for long periods often makes it worse. Most cases resolve within several weeks with conservative treatment, though severe or persistent sciatica sometimes requires more intervention.
Spinal Stenosis and Degenerative Changes
As you age, the spaces within your spine can narrow, putting pressure on the nerves that travel through them. This is spinal stenosis, and it’s more common after age 60. The narrowing happens gradually from years of wear, thickened ligaments, or bone spurs forming around the spinal canal. Symptoms often include back pain, leg heaviness, and cramping that gets worse when you walk or stand for a long time but improves when you sit down or lean forward.
Degenerative disc disease is another age-related change. Your spinal discs lose hydration and height over time, reducing their ability to cushion your vertebrae. This can lead to chronic stiffness and aching, particularly after sitting or first thing in the morning. Spondylolisthesis, where one vertebra slips forward over the one below it, produces similar symptoms. Women are somewhat more likely to develop spondylolisthesis, and the average age at diagnosis is in the mid-60s.
When It’s Not Your Spine at All
Not every pain in your lower back originates from your spine. Kidney problems, including infections and kidney stones, can produce pain that feels like it’s coming from your back. The key differences: kidney pain is usually felt deeper, in your sides or under your rib cage, and it often radiates toward your abdomen or groin rather than down your leg. It may come in intense waves rather than a constant ache, and it’s frequently accompanied by fever, nausea, blood in your urine, or pain when you urinate.
Spine-related back pain, by contrast, is usually centered over the middle of your lower back, worsens with movement or position changes, and may radiate into your legs. If your pain comes with urinary symptoms, fever, or nausea, the cause may be your kidneys rather than your muscles or discs.
How Long Back Pain Lasts
Doctors classify lower back pain by duration. Pain lasting less than six weeks is considered acute. Pain from seven to twelve weeks is subacute. Anything lasting three months or longer is chronic. Most acute back pain resolves without treatment, and imaging like an MRI or X-ray is generally not recommended unless your symptoms haven’t improved after six weeks of conservative care or you have warning signs of something more serious.
This timeline matters because it guides treatment decisions. For uncomplicated acute pain, the focus is on staying as active as you can tolerate, managing discomfort, and giving your body time to heal. If pain persists into the subacute phase, a more structured approach with physical therapy becomes more important. A clinical trial published in JAMA found that people who started physical therapy early (within four weeks of pain onset) had measurably better disability scores at three months compared to those who received usual care alone.
Managing Pain at Home
For the first few days of acute lower back pain, over-the-counter anti-inflammatory medications like ibuprofen or naproxen can reduce both pain and swelling. Apply ice for the first 48 hours to limit inflammation, then switch to heat to relax tight muscles and improve blood flow.
Movement is medicine for most back pain. Bed rest beyond a day or two tends to make things worse, not better. Gentle walking, stretching, and gradually returning to normal activity help your muscles stay conditioned and reduce stiffness. When sleeping, the side-lying position is generally the easiest on your lower back. Over 60% of adults prefer it, and for good reason: lying on your stomach offers the least support for your lumbar spine and can increase the curve in your lower back, loading the small joints along your spine.
Warning Signs That Need Immediate Attention
Rarely, lower back pain signals a medical emergency called cauda equina syndrome. This happens when the bundle of nerve roots at the base of your spinal cord becomes severely compressed, usually by a large disc herniation. The symptoms are distinct: sudden difficulty urinating or controlling your bladder or bowels, numbness in your inner thighs and groin area (sometimes called “saddle numbness”), and progressive weakness in one or both legs. This requires emergency surgery to prevent permanent nerve damage.
Other red flags include back pain accompanied by unexplained weight loss, fever, or pain that wakes you from sleep and doesn’t improve with any position change. A history of cancer combined with new back pain also warrants prompt evaluation, as does back pain following significant trauma like a fall or car accident.