This is a positional deformity where the entire foot is inverted relative to the ground when the subtalar joint is in its neutral position, as shown below.
This is by far the most common foot disorder we will see. Exists in about 85% of the patient population that has pronation problems. This is the positional deformity demonstrated as inversion of the rearfoot relative to the ground upon weightbearing in the posterior view. Non-weightbearing, uncompensated posterior view will show a varus angle between the midline of the lower 1/3 of the leg and the bisection of the calcaneus (refer to diagram). This deformity does not appear in a plaster slipper cast because the cast will only show the relationship between the forefoot and the rearfoot. The problem is not intrinsic to the foot. The problem is the inverted foot relative to the leg.
Three types of rearfoot varus are clinically seen.
- Uncompensated: The heel functions in an inverted position. The degree of tibial varum (bow leg) is greater than the amount of available calcaneal eversion through subtalar joint pronation.
- Partially Compensated: The heel functions inverted, but to a lesser angle than the total deformity. The degree of tibial varum is only slightly greater than the available calcaneal eversion.
- Compensated: The heel assumes a vertical position to the ground. Tibial varum is equal to the amount of available subtalar pronation.