During spinal flexion, what happens to the nucleus pulposus?

• A. Anterior compression and posterior displacement
• B. Posterior compression and anterior displacement
• C. Anterior tension and posterior displacement
• D. No change

Answer: (A)

When the spine flexes forward, the front (anterior) portion of the intervertebral disc is compressed while the back portion becomes relatively stretched. The nucleus pulposus acts like a hydrostatic gel inside the disc, so this anterior compression pushes the nucleus toward the posterior side. In short, flexion creates anterior compression of the disc and posterior displacement of the nucleus pulposus. The other patterns don’t align with how the nucleus redistributes pressure during forward bending.