  Pose Priors are critical in human pose estimation, since they are able to
enforce constraints that prevent estimated poses from tending to physically
impossible positions. Human pose generally consists of up to 22 Joint Angles of
various segments, and their respective bone lengths, but the way these various
segments interact can affect the validity of a pose. Looking at the Knee-Ankle
segment alone, we can observe that clearly, the Knee cannot bend forward beyond
it's roughly 90 degree point, amongst various other impossible poses below.

Robotics;Computer Vision and Pattern Recognition