The human spine degenerates—such is the nature of being alive. For many different reasons, from the moment we are born we are basically falling apart.
Aging is the most natural of our degenerative processes. As life goes on, our bones slowly dry up, becoming brittle to varying degrees.
Injuries and their compensations, illnesses, genetics, and other factors also affect how the spine holds up through life. These are all things that, for the most part, are outside of our conscious control. Posture is something within our control, and hyperextending the knees is one of the most common postural mistakes. My take is that poor posture is responsible for a good deal of spinal degeneration—and it tends toward a particularly insidious degeneration, because the subtle wear and tear from years—a lifetime—of bad posture and movement patterns often catch up to us later in life.
In an attempt to simplify the workings of a complex body, I like to say that the bones hold you up, the muscles move you, and the nerves tell the muscles to move the bones. In holding you up, the bones bear and transfer weight by stacking one directly on top of another. A well-aligned skeleton allows the muscles to work as little as possible to hold you up, which frees those same muscles to function as they were designed.
The movement of almost any joint in the body affects other joints both near and far (there is only one bone in the entire body, the hyoid, that doesn’t affect other joints with its movement). The optimal functioning of the spine requires all of the joints of the body to be working harmoniously together. This is easier said than done.
Hyperextension is the movement of a joint past its normal range of motion. In the case of the knees, this means that the shin bones are moved backward into an obtuse angle with the foot and ankle.
The shin, when standing, would like to be at a right angle to the foot. If weight is going to pass down through the spine to the pelvis, legs, and feet successfully, the femur bone needs to be situated directly above the tibia so that the tibia can be directly on top of the ankle (talus bone). A hyperextended knee joint moves these bones backward, diminishing the possibility of successful weight transfer. The alignment of the spine is highly dependent on the position of the pelvis, and it is very difficult to align the pelvis properly if the knees are hyperextended.
When the knees hyperextend the tibia, fibula, and femur move backward at the knee and the femur moves forward at the top of the thigh. This forward movement of the thigh pulls the pelvis with it, often, but not always, tucking it under. The spine is pulled out of alignment accordingly and the result is often a very subtle compression at the back of both the lumbar and cervical spine.
This is the insidiousness mentioned above. The hyperextension of the knees—or the misalignment of any joint, for that matter—does not have to be excessive; years and years of the most subtle misalignment will add up over time to compromise the whole skeleton, but especially the spine.
Spend some time today feeling your own posture and looking at people’s knees when they stand and walk.