The human knee has a screw home mecanism where the tibia goes in external rotation compared to the femoral condyles. The geometry of the tibial plateau makes it easier and effortless to stay standing with a locked knees in full extension.
When rubbing you never go into full extension because you need your knee to using biarticular muscles like the hamstrings and the gastrocnemius to bounce and recoil 17% if the energy stored in the buarticular tendon collagen for more effective bouncing while running.
Optimus will never had a normal gait if they don’t force it to walk like a human being. If they use actuation motors in the joints there is no reason to reproduce a screw home mechanism as the motors just lock the joint in the desired position without having a muscle or tendon to fatigue to keep a joint in a desired position from a prolonged period of time.
This was also a publication I have made and presented on during my masters degree in training so I had to share that useless knowledge I have not used for over a decade.
Thank you for listening to me