Leg-length inconsistency can be divided into two etiological groups:
1. Structural. True shortening of the skeleton from congenital, traumatic or diseased origins.
2. Functional. Development from altered mechanics of the lower body, such as foot hyperpronation/supination (Figure 1), pelvic obliquity, muscle/joint imbalances, poor trunk stabilization and deep fascial strain patterns.
Flawed feet and ankle structure profoundly affect leg length and pelvic positioning. The most common asymmetrical foot position is the pronated foot. Sensory receptors embedded on the bottom of the foot alert the brain to the slightest weight shift.
Most structurally oriented manual therapists have learned hands-on routines for separating adhesive fascial bags of the 11 lower leg muscles to lift (or lower) dysfunctional foot arches. To insure proper foot functioning, tone must be stimulated in weakened arch muscles using fast paced muscle spindle techniques. As the myofascia regains lost elasticity, blood flow and vital nutrients saturate the fatigued tissues, allowing the muscles of supination (tibialis anterior, peroneus longus, tibialis posterior, etc.) to regain strength and mobility.
Biomechanical Relationship of Feet to Pelvis
Figure 4. Coupling of Ilial Rotation and Leg Length Discrepancy
(Adapted from Mitchell F. Jr. The Muscle Energy Manual with permission).
Ilial rotation is united with leg length discrepancy. In Figure 4, the femoral head on the long leg side “drives” the ilia upward and backward. Conversely, the ilium on the low femoral head area drops down (anteriorly rotates). The concurrent rotation of both ilia in differing directions produces a left-on-left sacral torsion (Figure 5).
Now place your thumbs on each sacral base and change side to side. Right leg weight-bearing should make the right sacral base to go deep (anteriorly rotate).