The diagnosis of low back problems begins with a thorough history of your condition. Your doctor will ask you questions to find out when you first started having problems, what makes your symptoms worse or better, and how the symptoms affect your daily activity.

Your doctor may do some simple tests to check the function of the nerves. These tests are used to measure the strength in your lower limbs, check your reflexes, and determine whether you have numbness in your legs or feet. Doctors commonly perform a leg-raising test. You lie on your back, and the doctor lifts your straightened leg upward to see if and where you feel pain. This test is mainly used to check whether there is pressure or irritation of the spinal nerves in the lowest part of the spine.

The information from your medical history and physical examination will help your doctor decide which tests to run. Imaging tests help your doctor see the anatomy of your spine. There are several kinds of imaging tests:

• X-rays: Standard X-rays show problems with bones, such as infection, bone tumors, or fractures. They also show the amount of space in the neural foramen and between the discs. Unless the doctor suspects these problems, most patients don't require X-rays on their first doctor visit for low back pain.
• MRI scans: Magnetic resonance imaging (MRI) scans use magnetic waves to create pictures of the cervical spine in slices. The MRI scan shows the neck bones and soft tissue structures such as the discs, joints, and nerves. MRI scans are painless and don't require needles or dye.
• CAT scans: The CAT scan is a detailed X-ray that lets doctors see "slices" of bone tissue. It is used primarily when problems are suspected in the bones. A special dye is sometimes injected into the bloodstream before the CAT scan to help the doctor identify the spinal nerves.
• Myelography: Myelography is a special kind of X-ray test. A special dye is injected into the space around the spinal canal--the subarachnoid space. The dye shows up on an X-ray helping the doctor see if there is a herniated disc, pressure on the spinal cord or spinal nerves, or a spinal tumor.
• Discography: Dye is injected into one or more discs. The dye is seen on the X-ray and can give some information about the health of one or more discs.
• Bone scan: A bone scan involves injecting "tracers" into your blood stream. The tracers then show up on special X-rays of your back. The tracers build up in areas of extra stress and bone activity, such as a fracture.
• Electromyogram (EMG): This is an electrical test of the nerves going to the lower limbs. EMGs are done to determine whether the nerves are being pinched.
• Laboratory tests: Not all causes of low back pain are from degenerative conditions. Doctors use blood tests to identify other conditions, such as arthritis or infection.