Whiplash is a term used to describe the painful symptoms that can occur after the head and neck bend forward and back with force. Whiplash injuries occur most often with rear-end or side impact accidents. The energy transfer during the forceful movement is what causes the injury.
No findings doesn't mean there's no injury. Research shows the damage or injury is difficult to see with imaging studies. But there's no doubt that muscles, joints, and discs can be damaged. Not only that, but the inner ear, nerves, and even the brain and esophagus can be injured.
Tiny tears in these structures may be the underlying problem. We don't really know more than that at this time.