Fundamentals for Understanding Posture Control Insoles
To fully appreciate the simple approach discovered by Dr. Rothbart, one needs to understand the basic mechanics of pronation, hyperpronation, and how the body responds to hyperpronation.
Just like cholesterol, there are two kinds of pronation. As you would expect, one is good and necessary. The other is not! The necessary form of pronation originates from the hip and is normal and necessary for the foot to function correctly. It is invisible to the observer, but can be measured using sophisticated motion tracking equipment. During normal gait, as the hip rotates anteriorly in the transverse plane, the foot on the same side is caused to pronate to unlock the foot in preparation for heel strike. As the same hip rotates past it’s static position in a posterior direction, the same foot is caused to move toward supination in preparation for toe-off. Provided there are no motion distorting pathologies, this is the basic mechanics of normal and “good” pronation. Hip motion does not cause hyperpronation.
A second source of pronation, the “bad” pronation, originates from the foot; specifically from Rothbart’s Foot Structure (RFS), and is the cause of hyperpronation in common flexible arch feet. Hyperpronation is readily visible to the observer. As described previously, RFS implies that the first metatarsal and the big toe are not fully weight bearing when the patient stands naturally. As the weight is transferred to the forefoot during the normal gait, the first metatarsal and the big toe do not become fully weight bearing until the foot has hyperpronated sufficiently to make up for the elevation of the first metatarsal and the big toe. As is the case with severe hyperpronators, the first metatarsal and big toe never become fully engaged, and the weight is carried by the second metatarsal.
The medical definition of the medial column of the foot includes the first three metatarsals, but when related to Rothbart’s Foot Structure and hyperpronation, we have defined the medial column as the big toe (proximal phalanx and hallux), the first metatarsal bone, medial cuneiform, navicular, and talus; the bones that primarily are affected when the arch collapses. As the medial column collapses, the heel twists.
When the medial column collapses, the elevation of the joint surfaces supporting the tibia and fibula drops downward and changes angle and effectively transmits an imbalance to the pelvis. Hyperpronation also gives rise to torsional forces in the leg, which often affect the knee and hip.
Hyperpronation is not a condition which gradually occurs as we grow older. The effects hyperpronation has on the body, however, significantly increase with age and physical activity.
Understanding the biomechanical relationships of hyperpronation and the reasons for this common problem, provides for a logical approach to reducing its undesirable effects by utilizing a Postural Control Insole™ (PCI).
The PCI is designed to facilitate the angle of the medial column resulting from the incomplete untwisting of the bones.