In a young, otherwise healthy female presenting with low back pain and normal imaging, what is a very likely cause?

• A. Lumbar disc herniation.
• B. Facet arthropathy.
• C. Iliolumbar ligament trigger point/instability.
• D. Spondylolysis.

Answer: (C)

Localized axial low back pain in a young, otherwise healthy person with normal imaging is most often due to soft-tissue or positional factors rather than a structural disk or joint disease. The iliolumbar ligaments stabilize the lumbosacral junction, and irritation or myofascial trigger points in this area can produce focal low back pain without any abnormal findings on standard spine imaging. This pattern fits a patient who has pain confined to the lower back, may be aggravated by movement or loading, and does not show radicular symptoms or detectable disc or facet pathology on imaging.

Lumbar disc herniation typically causes leg pain or neurological signs and would be suspected if imaging revealed a disk extrusion or if there were radicular symptoms. Facet arthropathy tends to occur with aging and degenerative changes, making it less likely in a young patient with normal imaging. Spondylolysis can occur in young people, especially athletes, and may present with persistent axial pain; however, the combination of normal imaging and a presentation that often centers on soft-tissue stability and trigger points makes iliolumbar ligament–related pain the more likely cause in this scenario.