Low back pain is an ache or discomfort in the lower part of the spinal column. It may radiate down into one or both legs. The lower spinal column consists of small, stacked bones (the vertebrae) that surround and protect the spinal cord and nerves.

Cross-section of Vertebral Canal with Spinal Cord in the Center

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There are many possible causes for low back pain, including:

• Sprain or strain of muscles or ligaments in the area
• Herniated disc or ruptured disc—the cushions between the bones of the spine bulge out of place as a result of age-related changes or trauma.
• Disc degeneration—caused by arthritis or aging
• Lumbar spinal stenosis —bony narrowing of the spinal canal in the low back area
• Spondylolisthesis —slippage of one bone over another, causing stretching or pinching of nerves
• Fractures due to trauma or osteoporosis
• Fibromyalgia —a condition that causes muscle aches and fatigue
• Ankylosing spondylitis —a disorder that causes spine stiffness and arthritis (believed to be hereditary)
• In rare cases,
  • Benign or malignant tumors
  • Infections
  • Arterial problems, such as hardening of the arteries

Lumbar Disc Herniation With Pinching of Spinal Nerve

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Sciatica is irritation of the sciatic nerve. It leads to pain that starts in the lower back and spreads to the buttocks and down the back of each thigh. The sciatic nerve is composed of several nerve roots that start from the lower part of the spinal cord. These nerves form a network that lead to individual nerves. These nerve bundles travel deep in the pelvis to the lower buttocks. From there, the nerve passes along the back of each upper leg and divides at the knee into branches that go to the feet.

Anything that causes irritation or puts pressure on the sciatic nerve can cause sciatica, including:

• Herniated disc (ruptured or slipped disc)
• Disc degeneration
• Spinal stenosis
• Spondylolisthesis
• In rare cases:
  • Benign or malignant tumors
  • Infections

Low back pain is very common. Over the course of a lifetime, almost 80% of Americans will suffer from at least one episode of back pain. Every year, about 15%-20% of the adults in the United States will report back pain. Most back pain gets better with time. About 5% to 10% of patients will continue to have pain for longer than three months.