Lumbar Disc Herniation

A lumbar disc herniation is the most common cause of pain that travels down the leg — what most patients know as sciatica. Each disc between the vertebrae of the lower spine has a soft gelatinous center, the nucleus pulposus, encased in a tougher outer ring, the annulus fibrosus. When the outer ring tears or weakens, the inner core can push backward into the spinal canal and press against one of the nerve roots that exits at that level. The nerve root becomes irritated both by the mechanical pressure and by inflammatory chemicals released from the disc itself, producing pain that follows the nerve's path rather than staying in the back.

The levels most often affected are L4-L5 and L5-S1, which compress the L5 and S1 nerve roots — the nerves that feed the front and back of the leg down to the foot. Symptoms are classically worse with sitting, bending, and anything that raises pressure in the abdomen (a sneeze, a cough, straining on the toilet), because those movements push the herniated material harder against the nerve. The large majority of lumbar disc herniations resolve with nonoperative care as the displaced fragment shrinks and inflammation subsides — surgery is the exception, not the rule.

The signature symptom is pain that travels from your lower back into one leg — often described as a burning or electric-shock sensation that follows a specific path. An L5 nerve root compression typically sends pain down the outer calf to the top of the foot, while S1 compression travels down the back of the calf to the outer edge of the foot and sole. The leg pain is usually far worse than the back pain itself.

Sitting, bending forward, coughing, and sneezing tend to make the pain sharply worse because these positions push the disc material harder against the nerve. Numbness or tingling in the foot or toes, weakness when lifting the foot (foot drop) or rising on tiptoe, and relief when standing or walking are all common. Emergency: sudden loss of bladder or bowel control, saddle-area numbness, or bilateral leg weakness means a trip to the emergency department — not a clinic appointment.

Your surgeon will use the straight leg raise test — slowly lifting your leg while you're lying flat — which reproduces the leg pain when a lower-spine disc is compressing a nerve. MRI is the standard imaging test. Important nuance: many adults who have NO symptoms also have herniations on MRI, so the imaging finding has to match your specific symptom pattern to be the actual cause.

Most lumbar disc herniations resolve with a structured non-operative plan. Surgery becomes the right step for a small number of patients — typically those whose leg pain, weakness, or numbness has not improved after a genuine trial of care, or patients with red-flag findings such as progressive motor weakness or cauda equina syndrome (loss of bowel or bladder control), which is a medical emergency. When surgery is indicated, OSI coordinates it: imaging, records, and scheduling are handled for you.

Emergency. Bilateral leg weakness, saddle numbness, or loss of bladder or bowel control is a surgical emergency — go to the nearest emergency department rather than waiting for a clinic appointment.

External patient-education references and related OSI pages for additional background:

• Britannica — Herniated disc
• Britannica — Vertebral column
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language