Musculoskeletal strain: This is the most common cause of a swollen lower lumbar region, often resulting from overuse, heavy lifting, or sudden twisting movements, leading to inflammation and swelling of the muscles and ligaments.

Herniated disc: A herniated disc in the lower lumbar spine can cause swelling, pain, and discomfort in the affected area, especially if the herniation is compressing nearby nerves.
Degenerative disc disease: Wear and tear on the spinal discs can lead to inflammation, swelling, and pain in the lower lumbar region.
Spondylolisthesis: A condition where a vertebra slips out of place, potentially causing swelling and pain in the lower lumbar area.

Spinal infection (e.g., osteomyelitis, discitis): Infections of the spine can cause severe pain, swelling, and potentially life-threatening complications if not promptly treated.
Cauda equina syndrome: A serious condition where the nerves in the lower spine are compressed, leading to pain, swelling, and potentially permanent nerve damage if not urgently addressed.
Spinal tumor: Although rare, tumors in the spine can cause swelling, pain, and neurological symptoms, making prompt diagnosis and treatment crucial.

Epidural lipomatosis: A rare condition characterized by the accumulation of fat in the epidural space, potentially causing swelling and compression of the spinal cord.
Spinal epidural abscess: A rare but serious infection that can cause swelling, pain, and potentially life-threatening complications if not promptly treated.
Paget's disease of bone: A rare condition that can affect the spine, leading to swelling, pain, and potentially neurological symptoms due to bone deformities and fractures.