Pronation Primer: Part 2
The problem with OVERPRONATION
The consequence of under or over pronation ultimately means other articulations, including the spine, will have to attenuate more shock. Over time, this may lead to articular cartilage degeneration, disc degeneration, or ligamentous laxity, due to repetitive stresses.
What about assymetrical pronation?
It is rare that people over or under pronate the same amount on each side. Excess midfoot pronation on the right causes more internal rotation at the right knee (see above picture), and an increased valgus stress here. This puts the quadriceps at a mechanical disadvantage and stretches the adductor group, often making them stretch weak, and shortens the abductors, especially the gluteus medius, which often becomes short weak. The right foot, since it is now a poor lever, will often be externally rotated and toes claw, because the center of gravity has moved medially and they are trying to make that limb stable to bear weight on so they can progress forward. They will often toe off from the inside of the great toe (as is often evidenced by a pinch callus here). The medial rotation of the lower leg causes internal rotation of the thigh and anterior nutation of the pelvis on that side, both which now put the gluteus maximus at a mechanical disadvantage, limiting hip extension on that side. Now the extension has to occur to somewhere, so it often occurs in the lumbar spine, along with rotation and lateral bending to that side, increasing compression on the right facets. Now the vestibular system kicks in to right the head and we get contraction of the left paraspinals. Arm swing usually increases on the contralateral side to assist in propulsion forward. What effect do you think THAT has for about 10 thousand steps a day on spinal mechanics? What effect are we having on the nervous system and what neuroplastic changes are occurring? Hmmmm….
Having both feet planted on solid ground, or rather having both feet planted solidly on the ground should concern you. As you can see, knowing about pronation and its effects on the entire kinetic chain is paramount to the clinician. The effects reach far beyond the foot and can often be the root of recurrent biomechanical faults in the human frame.
And some people thought it was as easy as slipping an orthotic in there…
Yup, we still are….The Gait Guys