EE WAS PERFORMING AN EQUIPMENT SERVICE ON AN EXCAVATOR. HIS FOOT SLIPPED OFF STEP WHILE STEPPING DOWN FROM EXCAVATOR. (GREASE ON BOTTOM OF EE'S SHOES.) EE FELL ON GROUND. EE SUSTAINED A SPRAINED HIP, PER ORTHOPEDIC SPECIALIST. EE'S WORK AREA SHOULD HAVE BEEN MAINTAINED IN A CLEANER MANNER TO PREVENT GREASE FROM BEING ON SAFETY BOOTS.