oo that looks like fun, you need to place a CAT parent inside the knife, a pelvis at the base of the knife and make an arm run down to the other hand, make as many segments as there are in the chain and placed at their pivots, or only a few bones running down the chain, name the parts accordingly, create an IK target, set it to IK, add the skin modifier if you only used a few bone segments, if not you just link each segment to their own bones, link the pelvis and parent to the knife, and create a point helper and align it to the left IK target and link it to it, then link the chain IK target to the point helper and you should be good to go.