Lower back pain: when to worry, causes, and treatment

Most lower back pain is a muscle or ligament strain and improves within a few weeks with ordinary activity. Worry sooner, meaning same-day or emergency evaluation, when pain comes with leg numbness or progressive weakness, loss of bladder or bowel control, numbness in the groin or saddle area, fever, unexplained weight loss, a history of cancer, recent significant trauma like a fall or car accident, or pain that wakes you at night and does not change with position. Those combinations point to the rare causes that cannot wait. On the other end, pain after lifting or a long drive that is sore to touch, changes with movement, and slowly improves is the common kind. If you are somewhere between those two poles, a text consult is a quick way to sort out which side you are on.

The most common causes by far are muscle or ligament strain from lifting, twisting, a sudden awkward movement, or prolonged sitting with poor support, often after doing more than your back is used to. Other causes include a bulging or herniated disk pressing on a nerve, arthritis of the spinal joints, and sciatica, which is nerve irritation that sends pain, tingling, or numbness down one leg. Less often the cause is spinal stenosis, a compression fracture, infection, or a kidney problem, which is why back pain with fever or urinary symptoms deserves a closer look. Age, weak core muscles, excess weight, and smoking all raise the odds. The reassuring part: most episodes have no dangerous underlying cause and settle within weeks without any special testing.

Move. Every major guideline says staying active within your tolerance speeds recovery, while bed rest beyond a day or two weakens the muscles that support the spine and actually makes back pain last longer. Gentle walking is the single best activity in the first days. Keep doing normal daily tasks as tolerated, then add exercise back gradually over one to two weeks. What to avoid while the pain is acute: heavy lifting, repeated bending and twisting together, and long uninterrupted sitting, so stand up and walk briefly every half hour. Pain that stays tolerable and is not shooting down the leg with numbness is safe to move through; the body heals faster with movement than with waiting.

Usually not, and early imaging can backfire. MRI is reserved for red-flag situations, meaning suspected fracture, infection, cancer, or cauda equina syndrome, and for pain with persistent nerve symptoms like leg weakness or sciatica that has not improved after about 6 weeks of conservative care. The problem with scanning everyone is that most adults' spines show bulging disks and wear changes on MRI even when they have zero pain, so an early scan often finds something that was never the cause and pushes people toward injections or surgery they did not need. If your pain has none of the red flags, guidelines recommend treatment first and imaging only if it is not improving. A consult can check your red flags quickly if you are unsure.

For most acute lower back pain the evidence-backed plan is simple: stay active, use heat on the sore area for 15 to 20 minutes at a time, and take over-the-counter anti-inflammatories like ibuprofen if you can take them safely. That combination outperforms rest, and most people improve meaningfully within two weeks. If pain persists past a few weeks, physical therapy with targeted strengthening and mobility exercises is the next step and has the best long-term record. Opioids are not recommended for routine back pain, muscle relaxants add little for most people, and the large majority never need injections or surgery. New severe pain with any of the red-flag features is the exception and skips this whole ladder in favor of urgent evaluation.

Rarely, yes, and the serious causes each have a recognizable pattern. Cauda equina syndrome, where nerves at the base of the spine are compressed, shows up as leg weakness plus new bladder or bowel control problems or numbness in the saddle area, and it is a surgical emergency. Spinal infection usually pairs back pain with fever and feeling systemically ill. Cancer-related pain tends to be constant, worse at night, unaffected by position, and comes with weight loss or a cancer history. An abdominal aortic aneurysm can cause deep back or abdominal pain, typically in older smokers. Fractures follow significant trauma or occur with osteoporosis. The shared warning signs: fever, night pain that position changes do not ease, unexplained weight loss, history of cancer, recent major trauma, and progressive leg weakness. Any of those means get seen promptly.