In the hierarchy, I'd have the patella as a child of the tibia, rather than the femur. That way all that needs to happen joint wise is a little bit of posterior rotation to maintain distance from the femur during knee flexion. Looking at your examples, you may not even need that, except that the curve at the bottom of the femur where you have the patella inset, is not true to life, if you look at both of @quietrob's example images.

All of that said, however, I can't see anything that would stop me modifying the figure to my own stringent personal requirements with morphs. At least with a skeleton there's zero need to worry about joint zones and weight maps! Woo hoo! ;-) [Unless you want to bend cartilage]

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