EE WAS DESCENDING LADDER FROM ELEVATED LOADING PLATFORM TO TOP OF TANKER TRAILER TO CLOSE HATCHES SO TRUCKER COULD PRESSURIZE THE TRAILER. SAFETY LANYARD CAUGHT ON ROUGH SPOT ON HANDRAIL CAUSI NG EE TO BE JERKED CAUSING HIM TO LOOSE BALANCE.ATTEMPTING TO REGAIN BALANCE EE EXTENDED FOOT OUT & INTO OPEN HATCH OF TRAILER. THE SHIN OF RIGHLEG STRUCK EDGE OF HATCH. WOUND CLEANDED, STAPL