Physics of my Knee’s While Running
Throughout my life, I have been an athlete. Whether it’s team sports like soccer and basketball or individual sports like tennis and gymnastics, I have been active my entire life. These various activities have caused a variety of sports-related injuries in my life. Some of my injuries were so extreme that they caused my muscles and joints to compensate for pain by moving in new ways. An example of this is the way my hip and knee joints work while I run long distances. Instead of the 2D motion that most legs make while running (Figure 1), my knees act more like a ball in socket joint that can rotate in 3D such that my steps are in front of one another, but my tib-fib makes a whipping motion to the side between strides–similarly to Figure 2. As the knee is a hinge joint, this motion is very slight and therefore most people do not notice exactly what is off when they see me run from the side; they just can tell that my stride looks different. This altered motion is a result of my hips–an actual ball in socket joint–that rotate my femurs medially. This rotation causes my lower legs to get in the way of each other unless this whipping motion occurs. Overall this change in joint function causes my running speed to be decreased as the energy I put into my stride partially goes into the rotational motion of my knee joint.
Figure 1- 2D running motion
Figure 2- Ball in Socket Joint Rotation
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