I've seen that before. It usually takes a while but the most common way the PI undoes the fakers is getting video of the supposed injured party doing things that one wouldn't even attempt with a sore back. They had one with a claimant saying his back was completely disabled so the PI presented a video in court of the guy easily riding a jet ski when he was supposedly near paralyzed.
Howard Deane got out of going to Vietnam by claiming a bad back....then went skiing at Vail.