Most people recover from whiplash injuries within the first few months. However, some people have long term pain—lasting months or years. Until now there has been no way of diagnosing these more severe cases.

New research suggests that fat deposits in the neck muscles are the key.

“We’ve found that people with long term injury have large amounts of fat infiltration in their neck muscles,” says Dr James Elliott from the University of Queensland (and former US professional baseball player). “Something is causing that difference, and it isn’t their body weight,” he says.