Biomechanists use musculo-skeletal models to understand human movement. This knee-joint model is used to understand how the knee truly moves and how the knee changes with injury or disease – courtesy of the University of Wisconsin Neuromuscular Biomechanics Laboratory.
Here’s a model that includes the muscles and other soft tissue structures surrounding the knee.
Here’s a biomechanical model of a person walking – courtesy of Vanderbilt University.
Look! A foot in action – courtesy of The Spaulding National Running Center, Harvard Medical School.