In diagnosing a herniated disc, a physician will review a medical history and perform a physical examination. In addition, the physician may perform a straight–leg–raising test in which the patient lies flat and the doctor lifts each leg up. If the patient experiences pain in the back at certain angles, it may indicate a herniated disc.

A physician may also order an imaging test to help reveal the extent of damage to a disc and to rule out other possible sources for the pain, such as a spinal tumor or circulatory problems. Imaging tests that may be performed include x-ray, MRI  (magnetic resonance imaging) or CAT scan (computed axial tomography).

If noninvasive tests indicate a disc problem, the physician may order a minimally invasive imaging test to get information in greater detail. Discography is a type of x-ray involving an injection of contrast medium (dye) into the injured disc. In myelography, the dye is injected into the spinal canal.

Nerve tests such as electromyography (EMG) may also be performed. This can help detect signs of nerve damage resulting from a disc herniation, and can determine which nerve roots are involved. EMG uses electrodes placed on the skin or needles inserted into muscle to help determine function of nerves and muscles. It is often performed in conduction with nerve conduction velocity (NCV) studies, which use electrodes to measure the speed of nerve impulses.

Despite these tests, in many cases it may be difficult to determine whether or not a herniated disc is the source of a patient’s back pain. About one–third of all adults age 30 and older show signs of intervertebral disc abnormality due to natural degeneration, but in most cases this damage does not result in pain. Discography is considered one of the most useful tests to diagnose discogenic pain (pain originating from herniated disc).