I'm still having neck pain after a car accident. I had a friend tell me that this is because I had my head turned facing the driver when the crash took place. It sounds reasonable but what's the logic behind this explanation?
Long-lasting pain after a car accident from a whiplash injury occurs in a small number of people. But it can be very annoying, if not disabling. Scientists are actively studying this problem. It even has a name of its own now: whiplash-associated disorder or WAD.
It's not clear just what the source of pain is in WAD. Studies show that about half the time, the pain is coming from the facet (neck) joint. Injecting a numbing agent into the area relieves the pain. But since this doesn't explain all cases, there may be some other reasons as well.
Animal studies have shown there is an electrical response in the facet joint when a mechanical load is applied to the joint. This finding suggests that the capsular ligament has a threshold for pain. This means that pain occurs when the load (strain) placed upon it is above a certain level.
Human studies confirm that symptoms are much worse after the injury when the head was turned at the point of impact. This appears to be linked to the fact that the head-turned position puts a strain on the capsule normally. Any extra compression, load, or shear force can be enough to cause failure of the soft tissues.
It's likely that there are other explanations as well. The capsular ligament may have different mechanical tolerances at different locations within the ligament. So for example, multiaxial loads may affect the top front portion of the capsule more than the lower bottom half.
With the head in just the right position and with just the right amount of force, the ligament tensile strength may be overcome by the load. The result is injury to the ligamentous capsule. When the face is turned to the right, the right capsular facet is affected. When the face is turned to the left, the left side is injured.