Herniated Disk: The patient's history of a herniated disk and current symptoms of back pain, difficulty walking, and standing up are consistent with a herniated disk. This condition can cause nerve compression, leading to pain, numbness, and weakness in the back and legs.

Musculoskeletal Strain: The patient's back pain and difficulty walking could be due to a musculoskeletal strain, which is a common cause of back pain in young adults.
Degenerative Disk Disease: Although less common in young adults, degenerative disk disease can cause back pain and stiffness, especially if the patient has a history of trauma or repetitive strain.
Spondylosis: This condition, characterized by a defect in the pars interarticularis, can cause back pain and stiffness, especially in young adults.

Cauda Equina Syndrome: A rare but serious condition that occurs when the nerves in the spinal canal are compressed, causing numbness, weakness, and loss of bladder and bowel control. Prompt diagnosis and treatment are crucial to prevent permanent damage.
Spinal Infection (e.g., Osteomyelitis, Discitis): Infections of the spine can cause back pain, fever, and neurological symptoms. Delayed diagnosis and treatment can lead to serious complications, including paralysis and death.
Spinal Tumor: Although rare, spinal tumors can cause back pain, numbness, and weakness. Early diagnosis and treatment are essential to prevent neurological damage and improve outcomes.

Ankylosing Spondylitis: A chronic inflammatory disease that can cause back pain and stiffness, especially in young adults. Although rare, it's essential to consider this diagnosis in patients with persistent back pain and stiffness.
Spondylolisthesis: A condition where a vertebra slips out of place, causing back pain and stiffness. Although rare, it can occur in young adults, especially those with a history of trauma or repetitive strain.