Lumbar Disc Herniation: This is often the most common cause of low back pain with lower extremity symptoms, such as sciatica. The herniation of the disc can compress or irritate nearby nerves, leading to pain, numbness, and weakness in the lower extremities.

Lumbar Spondylosis: This condition involves wear and tear on the spine, which can lead to narrowing of the spinal canal (stenosis) and compression of the nerves, causing lower extremity symptoms.
Degenerative Lumbar Scoliosis: Abnormal curvature of the spine can lead to uneven wear and tear, causing pain and nerve compression symptoms in the lower back and extremities.
Lumbar Spinal Stenosis: Narrowing of the spinal canal can compress the nerves, leading to pain, numbness, and weakness in the lower extremities, especially with walking or standing.
Piriformis Syndrome: Compression of the sciatic nerve by the piriformis muscle can cause pain, numbness, and tingling in the buttocks and lower extremities.

Cauda Equina Syndrome: A serious condition where the nerves in the spinal canal are compressed, leading to severe pain, numbness, and weakness in the lower extremities, as well as bowel and bladder dysfunction. Prompt recognition and treatment are crucial to prevent permanent damage.
Spinal Infection (e.g., Osteomyelitis, Discitis): Infections of the spine can cause severe back pain and lower extremity symptoms, and if left untreated, can lead to serious complications, including paralysis and death.
Spinal Tumor: Tumors in the spine can compress nerves, leading to pain and lower extremity symptoms. Early detection is critical for effective treatment and prevention of long-term damage.
Abdominal Aortic Aneurysm: A ruptured or leaking aneurysm can cause severe back pain and lower extremity symptoms, and is a medical emergency requiring immediate attention.

Arachnoiditis: Inflammation of the membranes surrounding the spinal cord, which can cause severe pain, numbness, and weakness in the lower extremities.
Epidural Lipomatosis: A rare condition where excess fat accumulates in the spinal canal, compressing the nerves and causing lower extremity symptoms.
Tarlov Cysts: Fluid-filled sacs that can compress nerves in the spinal canal, leading to pain and lower extremity symptoms.
Spinal Epidural Abscess: A rare but serious infection that can cause severe back pain and lower extremity symptoms, and requires prompt medical attention to prevent long-term damage or death.