Acute Low Back Pain
Usually due to muscle strain, approximately 90% of patients with acute low back pain recover within 4 weeks without therapy. Further diagnostic work is not necessary unless there are red flags such as:
1) Possible fracture (major trauma, minor trauma in older patients or patients who may have osteoporosis).
2) Possible tumor or infection of a patient aged over 50 or under 20, a history of cancer, constitutional symptoms such as fevers, chills and weight loss, risk factors for spinal infection, recent bacterial infection, intravenous drug use or immunosuppression, pain that is worse when lying on back or severe night time pain.
3) Possible cauda equina syndrome: saddle anesthesia, bladder dysfunction, severe or progressive neurologic dysfunction in the legs, lax anal sphincter, major motor weakness in quadriceps (knee extensors), ankle plantar flexors, evertors, and dorsiflexors (foot drop).

Chronic Low Back Pain
A lifetime of poor posture and poor lifting and bending habits may stress ligaments posterior to the intervertebral disk to the point that even a minor stress precipitates a herniation and low back pain. Always bend with your knees, not your back.

Most medical physicians rely too heavily on diagnostic tests, especially for low back problems. As a consequence, many patients that suffer from low back pain do not find relief: the tests may show that little is wrong, or show abnormalities that are not the cause of the problem. In one magnetic resonance imaging study of 98 people, none of whom had back pain, bulging disks were detected in 52% at one or more intervertebral disks and 27% had protrusions. These findings emphasize the importance of matching test results with the patient's description of symptoms before contemplating surgery. Some specialists recommend being very conservative in managing patients with back pain. Before ordering an MRI there really should be a reason.

Sciatica, pain along the large sciatic nerve that runs from the lower back down through the buttocks and along the back of each leg, is a relatively common form of back pain.

Sciatica is usually caused by pressure on the sciatic nerve from a herniated disc (also referred to as a bulging disc, ruptured disc or pinched nerve). Other common causes include lumbar spinal stenosis, degenerative disc disease, priformis syndrome or isthmic spondylolisthesis. A little more detail about this is provided below. The problem is often diagnosed as a radiculopathy, meaning that a disc has protruded from its normal position in the vertebral column and is putting pressure on the radicular nerve root.

For some people, the pain from sciatica can be severe and debilitating. For others, the pain might be infrequent and irritating, but has the potential to get worse. Usually, sciatica only affects one side, and the pain often radiates through the buttock and/or leg.

One or more of the following sensations may occur:

• Pain in the buttocks and/or leg that is worse when sitting
• Burning or tingling down the leg
• Weakness, numbness or difficulty moving the leg or foot
• A constant pain on one side of the buttocks
• A shooting pain that makes it difficult to stand up

While sciatica can be very painful, it is rare that permanent nerve damage will result. Many pain syndromes result from inflammation and will get better within two weeks to a few months. Nerve pain is caused by a combination of pressure and inflammation on the nerve root, and treatment is centered on relieving both of these conditions.

Sciatica is a descriptive term and not an actual diagnosis for the underlying condition that is causing the pain. Lower back conditions that can cause sciatica include:

• Disc herniation - the soft inner core of the disc presses through the fibrous outer core of the disc and the bulge places pressure on the nerve root.
• Spinal stenosis - the facet joints become enlarged and place pressure on the nerve roots as they exit the spine.
• Degenerative disc disease - as discs degenerate, the inflammatory proteins from inside the disc can become exposed and irritate the nerve root.
• Isthmic spondylolisthesis - the nerve root can get pinched through a combination of the disc space collapse, fracture, and the vertebral body slippage associated with this condition.
• Piriformis syndrome -The sciatic nerve can get irritated as it runs under the piriformis muscle in the buttocks. Further information and exercises to help can be found here.
• Sacroiliac joint dysfunction - the sacroiliac joint can also irritate the L5 nerve, which lies on top of it, and cause sciatica.

Symptoms that may constitute a medical emergency include progressive weakness in the legs or bladder/bowel incontinence. Patients with these symptoms should seek immediate medical attention.