EMPLOYEE WAS TRYING TO RELIEVE PRESSURE ON A HYDRAULIC SYSTEM ON THE AUXILARY CRUSHER BY TAKING THE FITTING OFF A CYLINDER. EMPLOYEE DID NOT VERIFY THAT ALL THE PRESSURE WAS EXHAUSTED FROM THE HYDRAULIC SYSTEM. WHEN THE EMPLOYEE ATTEMPTED TO REMOVE A HYDRAULIC HOSE THE COUPLING KICKED BACK AND CAUSED AN INJURY TO THE EMPLOYEE'S RIGHT HAND.