Low back pain is one of the most common reasons for visiting a primary care physician. People may experience back pain after lifting heavy objects, twisting and turning their backs during exercise or household chores, or after a period of inactivity. Acute low back pain is often caused by muscle inflammation and spasm and may start suddenly or increase gradually over time. It may occur in the center of the low back or next to the spine on either side. The pain from muscle strain and spasm is often achy and crampy with periods of sharpness that occur because of "stressing" the involved muscle. Laying down usually relieves the pain. The pain is often accompanied by stiffness when moving the lower back and very tender muscles. It will usually get better with regular use of rest, heat, massage and/or anti-inflammatories and/or muscle relaxants for two to four weeks. Moist heat applied for 20 minutes three to four times daily and taking 200 to 800 mg per day of ibuprofen helps relieve the contracted and inflamed muscles. People can hasten recovery by continuing to be as active as tolerated and not to lift heavy objects or move in ways that aggravate the pain.

Low back pain which lasts more than 6 weeks and/or begins to change in character needs to be evaluated by a physician. If the pain becomes sharp and begins to radiate into the buttocks or down the legs, a nerve may be pinched. The most common nerve affected by muscular spasm, spinal stenosis or a herniated disk is the sciatic nerve. The sciatic nerve is a combination of nerve roots which come from the lower spinal cord (L4-S3) and form the largest nerve in the body. When a combination of the nerve roots or the whole nerve is pinched, one experiences pain, tingling or numbness in the buttock or the backside of the leg past the knee to the foot. One may notice the affected leg is weak and have foot drop or the inability to extend the great toe. Although pain caused by a pinched sciatic nerve (sciatica) can be very painful and debilitating, there is no risk of permanent nerve damage or paralysis. Sciatica is treated with physical therapy, massage, anti-inflammatories and manipulative treatments.

A herniated disk or narrowed spinal column (spinal stenosis) can also cause low back pain. The pain is achy or sharp and can worsen suddenly if nerves are compressed, leading to the symptoms discussed above. A primary difference between these conditions is that the pain from a bulging disk is made worse from bending forward and decreased by leaning backward. The opposite is true for spinal stenosis pain. The pain from both of these conditions gets better with laying down. Thee pain caused from sciatica is usually is not relieved by laying down (it may even get worse). The development of sudden leg weakness, lack of sensation in the pelvic area and involuntary leakage of urine or stool are signs of cauda equina syndrome. The cauda equina is a "tail" of nerves at the end of the spinal cord. If these nerves are pinched, it produces the cauda equina syndrome. In addition to the conservative treatments for a pinched nerve, surgery may be an option to reduce the impingement by removing the disk or fusing the vertebrae to widen the spinal column.

Other non-muscular and non-neurologic causes of back pain are infection and cancer. Warning signs that these conditions may be a cause of acute or chronic low back are fever, chills, lack of improvement with regular use of anti-inflammatories and exercise, and pain that worsens with laying on the back. It is important to inform a physician about these symptoms so that blood tests and imaging studies can be ordered to diagnose and treat these conditions before complications arise.

The injury associated with low back pain can be prevented by regular exercise (such as walking and low back exercises), maintenance of a healthy body weight and using correct body mechanics when lifting heavy objects.