Leg length discrepancy, or as it has been alternatively termed, the short leg syndrome, is by far the most important postural asymmetry. Limb length discrepancy is merely defined as a condition where one leg is shorter than the other. If a substantial difference exists, disruptive effects on gait and posture can occur.
Leg-length difference can be divided into two etiological groups:
Structural. True shortening of the skeleton from congenital, traumatic or diseased origins.
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.
Faulty feet and ankle structure profoundly affect leg length and pelvic positioning. The most familiar asymmetrical foot position is the pronated foot. Sensory receptors embedded on the bottom of the foot alert the brain to the slightest weight shift. Since the brain is always trying to maintain pelvic balance, when presented with a long left leg, it attempts to adapt to the altered weight shift by dropping the left medial arch (shortening the long leg) and supinating the right arch to lengthen the short leg.1 Left unchecked, too much foot pronation will internally rotate the left lower extremity, causing excessive strain to the lateral meniscus and medial collateral knee ligaments.
Conversely, excessive supination tends to externally revolve the leg and thigh, creating opposite knee, hip and pelvic distortions.
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 fill the fatigued tissues, allowing the muscles of supination (tibialis anterior, peroneus longus, tibialis posterior, etc.) to regain strength and mobility. In addition to myofascial work, one also must center attention on restoring alignment and motion to the subtalar joint commonly stuck in a valgus (pronated) position (Figure 2). The subtalar or talocalcaneal joint forms the articulation where calcaneus and talus convene and allows foot inversion and eversion. To bring back normal subtalar alignment, the therapist decompresses, abducts, plantar flexes and inverts the foot using myoskeletal contract-relax-assist (CRA) maneuvers. After successfully mobilizing the talus and calcaneus, all remaining ankle and foot joints should be systematically assessed and corrected.
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 top of the low femoral head area drops down (anteriorly rotates). The concurrent rotation of both ilia in opposite directions produces a left-on-left sacral torsion (Figure 5). This complex ilial rotation coexisting with sacral rotation usually is portrayed as pelvic obliquity. Weight bearing on the right leg will make this common compensatory pelvic pattern. Ilial rotation can be palpated by placing your fingers beneath each ASIS and shifting weight from one leg to another. 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).