EMPLOYEE WALKED THROUGH A PRODUCT SPILL THAT LED TO THE ENTRY TO A CONVEYER BELT WHICH CONCEALED A LARGE STONE. HE STEPPED ON THE STONE AND TWISTED HIS RIGHT ANKLE AS HIS FOOT ROLLED OFF THE S TONE. EE HAD HIS RIGHT KNEE ON THE GROUND CAUSING A CONTUSION OF THE KNEE. EMPLOYEE WAS TREATED BY A MD AND RELEASED TO RESTRICTED DUTY.