Compression or irritation of a nerve root by a herniated lumbar disc may lead to nerve root stress provocation, which in turn may cause symptoms such as pain and motor deficits in the lower extremity portion dominated by that nerve. The severity of leg pain from a herniated lumbar disc varies depending on the degree of nucleus pulposus irritation or compression of the nerve root. If the herniated disc simply irritates the nerve root, the condition is mild; if the herniated nucleus pulposus severely compresses the nerve root, which may lead to nerve paralysis or loss of function, resulting in abnormal pain in the leg or even inability to move the entire leg, the condition is more severe.