Our knees, the joints in our fingers, & our elbows are “hinge” joints—-similar to door, window, etc. hinges---meant to move in one geometric plane.
Introducing a rotating force in these joints causes injury, sometimes mild with a relatively easy recovery, but sometimes serious sprains that are not only difficult to recover from, but may leave lasting damage to the joint tissues.
Another force these joints are not meant to tolerate is hyperextension. Taking a hinge joint past its end point of tolerance for extension will cause injury. I often see this in patients who have propped their heel on a stool or ottoman, causing hyperextension of the knee.
Lateral forces such as sometimes happen in football to players’ knees, often also injure & can permanently damage a hinge joint.
