I must temper your optimism a bit though.
The knee surgeon was very worried about the chondropathie of the knee disc. Because that is not solved by a knee replacement joint.
So I have to try to grind the backside of the kneecap as much as I can by myself. Byclicling is f.i. a recommended training; but it has to be done with care. It can worsening the kneedisc also.
Twenty years ago I've made and designed my own recumbent bike from aluminium. It's a socalled low rider with a backseat that is ofcourse 100% modelled for me. Moreover It has also frontwheel suspension and backwheel suspension
so its chockfree.
Last week I mounted a chinese E-motor in my bracket with which I can control precisly the pedal force which I have to add.
See the motor upfront and the battery behind my head.