The pilot reported that he was flying the airplane while wearing an "air cast boot", during landing, the airplane decelerated, and he asked the passenger to move his feet up to the brake pedals and apply the brakes. He added that the passenger applied "insufficient differential brake application was applied" and the airplane veered left. The passenger applied right brake and rudder to correct, the airplane then veered to the right, exited the runway, and impacted a ditch. The pilot reported that he was wearing the boot due to a previous injury. He added that he had the ability to fully manipulate both rudder controls, but the boot prevented him from being able to fully apply brake pressure. The airplane sustained substantial damage to the right wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The automated weather observation station located on the airport reported that, about 31 minutes before the accident, the wind was from 340° at 6 knots. The same automated station reported that, about 29 minutes after the accident, the wind was from 330° at 7 knots. The airplane landed on runway 02.