The source of pain after whiplash injuries remains a mystery. Researchers are getting closer to solving the puzzle, but don't have all the answers yet.
In one study at Yale University School of Medicine, scientists confirm that joint sliding and compression cause injury of the nearby soft tissues. The cartilage, synovium, and nearby ligament are in danger of inflammation.
The nerves and blood vessels to the area become sensitive. This causes pain with normal motion. Damage to the joints can also cause neck muscles to misfire and contract at the wrong time. Over time, this change in normal firing patterns causes pain and spasm.
The force of the impact does make a difference. In other words, the greater the force, the more likely damage will occur. A minor impact may have the same effect as a higher force if there is arthritis present or some other damage from prior injury or accident. It's just a guess and hasn't been proven yet.