<p>Degenerative diseases of the lumbar spine are a common cause of chronic low back pain and neurological dysfunction. Their pathological basis involves not only microscopic structural damage to the intervertebral discs but also microscopic injury to adjacent nerves and muscle tissues. Diffusion tensor imaging (DTI), which relies on the anisotropic properties of water molecule diffusion, enables non-invasive, quantitative assessment of microscopic structural changes in intervertebral discs, nerve fiber bundles, and muscle tissues. Studies have shown that DTI-related parameters—fractional anisotropy (FA), apparent diffusion coefficient (ADC), and other parameters show a strong correlation with the degree of degeneration, nerve compression, and clinical symptoms in lumbar degenerative diseases such as intervertebral disc degeneration, lumbar disc herniation, and stenosis of the spinal canal and intervertebral foramen. These parameters can provide imaging evidence for identifying the affected segment and evaluating treatment efficacy. This review summarizes the recent advances in the application of DTI in lumbar degenerative diseases, with the aim of providing a reference for the clinical application of DTI and future research.</p>