One of the few tissues in the spine that can be implicated with some degree of confidence as the patient's source of pain is the nerve root. When the nerve root is involved in the pain syndrome, a very distinct set of symptoms and/or signs is present. There are two nerve root conditions: nerve root compression and nerve root irritation. Nerve root compression can result in true neurologic findings such as muscle weakness, reflex changes, and/or sensory disturbances. Nerve root irritation, which is often due to the abnormal chemical milieu that results from intervertebral disc lesions, presents with a distinct set of symptoms (as opposed to signs). Symptoms of nerve root irritation include: leg pain greater than back pain, clearly demarcated region of lower extremity pain, pain often below the knee, a highly disturbing and distressing type of pain, reproduction of lower extremity pain with neural tension tests (especially positive straight leg raise), and sharp peripheralizing pain with gentle spinal motions. Common examples of the latter include sharp and rapidly peripheralizing pain into the legs with slight degrees of active or passive lumbar flexion, or lumbar rotation of the lumbar spine. Any direction of motion can result in peripheralization of true nerve root irritation. The hallmark is the remarkably small amount of motion necessary to elicit such a dramatic pain response.