Hand rigging and animation problems

I’m having trouble with the fingers of the hand. specifically the knuckles. im having trouble rigging them to look realistic or at least good when animated.

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i’ve tried working with shape keys(i’ve only worked on the index finger, and the shape keys are only on the last 2 joints). i have enough problems trying to get it to look good stationary, but moving is terrible and forget about making a fist, which i cant make even though i modeled the entire hand to reference and i know the lengths of the joints and the finger all together are realistic.

quick reply is greatly appreciated.