Foot Shape Assessment

In order to identify natural foot shape variations, it is necessary to align the foot in its' neutral position, where the sub-talar joint is neither pronated or supinated.

Because of the role that the Sub-Talar Joint plays in the function of the foot, controlling the degree of pronation and supination through the Gait Cycle, finding the foot's neutral position means ensuring that this joint is neutrally aligned.

Sub-Talar Joint Neutral
Placing the Sub-Talar Joint in neutral reveals the natural alignment of the foot.

In the design blueprint for the human body, when the sub-talar joint is placed in it's neutral position, the alignment of the foot will be ideal. Where this is the case, both of the following will be true:

a) The vertical bisection through the calcaneus is in line (parallel) with that of the lower leg;

b) The horizontal plane of the forefoot is at 90 degrees (perpendicular) to that of both the calcaneus and lower leg and is parallel to the ground surface.

Any insufficent or excessive torsional untwisting of the calcaneus and/or talus will be evident as a varus (twisted inward) or valgus (twisted outward) deformity within the rearfoot and/or forefoot respectively.

Finding Sub-Talar Neutral Assessment
With the patient lying on their back (supine) and with their feet free of the end of the table, the Sub-Talar Joint is placed in neutral. The position of the rear and fore of each foot is then measured (usually by eye), relative to the vertical and horizontal respectively.

A very rough and ready guide to assessing footshape is to stand on one leg or lie down and shake the free leg and foot around to loosen the muscles. Allow the foot to come to rest naturally, and then have someone look at the position in which the foot naturally falls.

Example of Sub-Talar Joint Neutral Assessment

NOTE: It is not necessary, or recommended that actual degrees of misalignment are calculated from a Sub-Talar Joint Neutral Assessment. It is the relative angular relationships between the four quarters of the foundation that are important, not the actual angular position of each. Approximate degrees are shown in this example merely to aid understanding of the principles.

From the above example of a severe bilateral varus footshape (author of Root2Being), the following deductions can be made:

• The left foot is the most severely affected, where torsional untwisting of the calcaneus (rearfoot) and talus (forefoot) stopped approximately 25 and 30 degrees short respectively of their ideal alignment;
• The relative forefoot varus (difference between the forefoot and reafoot varus on the same foot) is greater on the right (approximately 10 degrees) than the left (approximately 5 degrees). This is represented by a more developed bunion on the right compared to the left;
• The actual (degrees of) forefoot varus on the right is less than that on the left.