EE WAS HELPING CHANGE A WHEEL UNIT ON A 21-SC. HE WAS PUSHING ON A LONG HANDLE BREAKER BAR WITH HIS FOOT. WHEN THE BOLT BROKE LOOSE, THE BREAKER BAR HANDLE MOVED CAUSING HIS KNEE TO TWIST CAUS ING THE INJURY. HE WORKED UNTIL 1/30/01. HE THEN WENT TO THE DR AND WAS TOLD TO TAKE OFF WORK.