Causes of protruding L4 and L5 discs include aging, poor posture and being overweight, notes the Laser Spine Institute. These conditions can result in lumbar disc disease, which occurs in the lower back. Most cases of the disease happen in the disc between the L4 and L5 areas, explains Johns Hopkins Medicine.
Lumbar spine discs lie between two of the five segments that comprise the bony part of the spine, according to Johns Hopkins Medicine. These discs contain two parts: the annulus fibrosis and the nucleus pulposus. The annulus fibrosis forms a circle of fibrous tissue around the gelatinous inner material of the nucleus pulposus. As a person ages, a disc may lose its fluid and dry out. The disc compresses as this happens, which can lead to deterioration of the annulus fibrosis. If this occurs, the nucleus pulposus bulges out, resulting in a bulging disc. If a disc continues to deteriorate, the nucleus may actually erupt through its outer layer. This is known as a herniated, or ruptured, disc.
Symptoms usually occur once the disc protrudes out enough to touch a nerve root. One of the most common symptoms of lumbar disc disease is sciatica, or an inflammation of the sciatic nerve. Sciatic pain begins in the lower back and can radiate through the buttocks, leg and calf, and even travel to the foot, notes Johns Hopkins Medicine. Other symptoms of herniated or bulging discs include numbness, weakness or a change in sensation. Although aging is usually the cause of protruding discs, avoiding some activities can slow down their development, states the Laser Spine Institute. Use good posture, especially when lifting; exercise regularly; and avoid being overweight.