Just to reiterate what was already mentioned in the Instagram post: the left AIC has some very typical presentations throughout the body. One such presentation is of a left foot that looks more pronated and a right foot that looks more supinated.
In reality, these feet are not truly pronated nor supinated. They are simply being forced, or directed, into “fake” pronation and “fake” supination by the left AIC patterned pelvis above it.
When a pelvis is stuck in a left AIC pattern, the entire pelvis is oriented to the right. This pelvis position shifts the body’s center of mass over to the right. If you were to stand up and orient your pelvis to the right, you should feel your weight shift to the right, and may feel your weight move to the outside of your right foot. This results in the appearance of a supinated right foot.
On the left side, the left leg orients internally along with the acetabulum of the left side of the pelvis. In this position the left foot is being directed into a flattened position that resembles pronation. But again, it’s fake pronation. The left foot is being forced into this position by the position of the leg and pelvis above it.
What People Will Feel
If I ask someone what they feel in a standing position– where they feel their weight on their feet– they will most likely say their left arch area and their right heel/lateral border.
What they don’t feel, and this point is the most important point, is their left heel and right arch.
This means that they don’t get left heel strike as their left foot hits the ground, so their left hamstring doesn’t activate to pull the left pelvis backwards and initiate left AF/IR. Instead they go straight to pronation. But in this case it’s still fake pronation because it was never preceded by heel strike. Pronation is an active process that requires heel strike to occur just before it. A foot that is already pronated can hardly be said to pronate in the truest sense of the word.
It also means that they don’t ever truly pronate their right foot. They go from heel strike, skip over pronation, and go straight to toe off. Without pronation the right side of the body never truly de-loads because the right glute max isn’t recruited to “push” their center of mass over to the left.
Both of these events, left heel strike and right pronation/toe-off have to occur appropriately to shift to the left and stay on the left side in true left stance position.
If people never over-ride this patterned foot position, which really reflects the position of the pelvis above it, they will stay stuck in right stance.