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Whiplash Symptoms Come From Increased Joint Motion

Neck pain and headaches are common after whiplash injuries. Symptoms can last months to years. The exact injury mechanism is still unknown. Researchers have shown it's not damage to the muscles or nerves. In this study scientists test the lower cervical (facet) joints as the possible source of chronic pain.

Cadavers were used to compare the load placed on the facet joints at the C4-C5 level. A special testing device was used to extend the neck with compression to mimic normal motion and whiplash injuries. Loading conditions for normal motion was compared to load during whiplash. Motion was measured for these two circumstances, too.

They found that when the neck was extended, the facet joints moved faster and with greater shear force under whiplash load. Although the segment didn't extend more between normal and whiplash conditions, the amount of facet joint motion increased with whiplash. They also saw that the increased facet joint motion causes greater joint capsule distortion along the front of the spine.

The authors say this is the first study to show in measurable terms the impact of whiplash on lower cervical facet joints. There's too much shear motion for the amount of extension.

Abnormal loading does affect the joint and the joint capsule. Joint capsule strain can result in chronic, painful whiplash symptoms.

References: Brian D. Stemper, PhD, et al. Localized Cervical Facet Joint Kinematics Under Physiological and Whiplash Loading. In Journal of Neurosurgery: Spine. December 2005. Vol. 3. No. 6. Pp. 471-476.

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