system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do most of the 4-leg robots (see: Boston Dynamics) have their knees look backwards?
gpt
Because they are not knee, they are Ankles.

The robot reproduce the articulation of a 4 legged animal. Human are bipedal so we use our heel and toes to walk and run. 4 legged animal usually only use their toes to walk and the ankle is higher and help to run.