a really anoying knock

i am really getting frusterated with this problem. anytime i change direction while moving slow i get a really bad knock. its a one time thing everytime i turn, stop, or go. i have been under the car pushing and pulling on everything. i have torqued everything. its not cv joints or lugnuts. it doesnt have anything to do with the engine. its also not my jack rolling around in the back. someone said that once. i feel it in the floor. i have never felt it in the steering wheel. it a 91 civic hatchback. any help would be greatly appretiated.