Mechanical Lower Back Pain: This is the most common cause of lower back pain without radicular symptoms, often related to muscle strain, poor posture, or overuse. It is typically characterized by pain that is exacerbated by movement and relieved by rest.

Degenerative Disc Disease: A common condition where the spinal discs lose their cushioning ability, leading to pain and stiffness in the lower back.
Spondylosis: A condition characterized by degenerative changes in the spine, including the facet joints and discs, which can cause lower back pain.
Musculoskeletal Strain: Acute or chronic strain of the muscles and ligaments in the lower back, often due to lifting, bending, or sudden movement.

Cauda Equina Syndrome: A rare but serious condition where the nerves in the spinal canal are compressed, leading to severe pain, numbness, and potentially permanent nerve damage if not promptly treated. Although it often presents with radicular symptoms, early stages might not.
Spinal Infection (Osteomyelitis, Discitis): Infections of the spine that can cause severe back pain, fever, and potentially serious complications if not treated.
Spinal Tumor: Tumors in the spine can cause back pain, and while rare, they are critical to diagnose early for effective treatment.
Abdominal Aortic Aneurysm: A potentially life-threatening condition where the aorta enlarges, which can cause lower back pain, especially if it is leaking or rupturing.

Spondylolisthesis: A condition where one of the vertebrae slips out of place, which can cause lower back pain.
Osteoporotic Compression Fracture: A fracture of the vertebrae due to osteoporosis, which can cause sudden onset of lower back pain.
Paget's Disease of the Bone: A chronic condition that can result in enlarged and misshapen bones, leading to pain and potential deformity.
Fibromyalgia: A long-term condition characterized by widespread pain in the muscles and bones, fatigue, and areas of tenderness, which can include the lower back.