When you position the weight bearing foot in neutral by palpating the subtalar joint for symmetry, you will find that in 80% of the population, the second, third, fourth and fifth metatarsal heads are on the ground. The first metatarsal and big toe is up in the air.
When you release the foot to a natural weight bearing position, the first metatarsal and big toe will have to travel a distance downward to become weight bearing, and in the process, the medial column of the foot collapses. The longitudinal arch collapses and the ankle rolls in.
When the medial column of the foot collapses, a whole chain (kinetic chain) of events is set off:
- Internal rotation of the lower extremities force the knees inward
- Internal rotation of the legs rotate the pelvis forward
- The center of gravity shifts forward as the upper body slumps forward
- Shoulders protract, upper extremities rotate internally and thumbs point inward
- Head shifts forward
You know the rest of the story... poor athletic performance, pain, troublesome patient management and so on. [ Ok, then what? ]