EE WAS RIDING A SCOOP USED TO HAUL EMPLOYEES TO THE TRACK. HE WAS IN THE SCOOP BUCKET AND SCOOP RAN OVER A ROCK CAUSING EE TO LOOSE HIS BALANCE. RIGHT LEG CAME OUT OF BUCKET AND WAS TWISTED UN DER BUCKET. EE WAS DIAGNOSED WITH A SPRAINED KNEE BUT CONDITION WORSENED AND EE WAS PLACED ON RESTRICTED DUTY ON 1-15-04. EE MISSED NO WORK AND PERFORMED REGULAR DUTIES UNTIL THEN.