Short Legs and the Crooked Pelvis

by Erik Dalton, Ph.D.

corkscrew

For efficient locomotion, a symmetrical and well-aligned body is essential. When the three bones of the pelvis are distorted by limb length discrepancies, gravitational forces wreak havoc on stretch-weakened SI joint and accessory pelvic ligaments (sacrotuberous and iliolumbar). These structures find themselves desperately struggling to maintain posturofunctional balance.

junctions

Left untreated, a diverse array of symptoms appears as the short leg destabilizes the pelvis by unleveling the sacral base (Fig 1). Painful lumbar compensations often travel all the way up through the occipitoatlantal (O-A) joint, as the spinal column is forced to rotate and side-bend to accommodate the crooked sacral base (Fig 2).

I often get asked how a leg length discrepancy can cause pelvic rotation and possible SI joint irritation. In Fig 3, the femoral head on the long leg side "drives" the ilia upward and backward. Conversely, the ilium on the low femoral head side drops down (anteriorly rotates). The concurrent rotation of both ilia in opposite directions produces a left-on-left sacral torsion (Fig 4).

long leg side

The combination of ilial rotation and sacral torsion causes compensatory lumbar scoliosis as the pelvis side-shifts left (Fig 5). Weight bearing on the right leg will produce this common compensatory pelvic pattern.

Experiment by placing your fingers under each ASIS and shifting weight from one leg to another. As weight is shifted over the left leg, the right ilium anteriorly rotates (drops inferiorly) and the left posteriorly rotates. Now place your thumbs on each sacral base and see if you can feel the sacrum rotate as you shift weight side-to-side. Left leg weight-bearing should cause the right sacral base to go deep (anteriorly/inferiorly rotate).

Some authors suggest that there is a rotation of the pelvis toward the long leg side, possibly due to hyperpronation and medial leg rotation.1 Walking on the toes on the short side and flexing the knee of the long side seems to be a fairly consistent compensatory movement pattern. As the center of gravity unevenly shifts, the smooth sinusoidal motion of gait is disrupted. Thus, the cosmetic effect of walking also can contribute to the compensatory mechanism and eventual injury. For example, walking on the toes can lead to contracture of the Achilles and calf muscles, creating conditions such as Achilles tendinitis and plantar fasciitis.

Plumb Line

Other functional scoliotic compensations include shortening of the quadratus lumborum on the long side, and a shortening of scalene, levator scapulae, sternocleidomastoid, and upper trapezius muscles on the contralateral side. This typical adaptive muscle imbalance pattern helps maintain erect head position with eyes level. But, prolonged muscle shortening "crams" vertebral and rib articulations, compounding the problem. Thus, a vicious pain/spasm/pain cycle sinks its neurological tentacles deep into old intrinsic spinal groove muscles (rotatores, multifidus, intertransversarii and levator costalis), resulting in central nervous system overload, limbic system hyperactivity. . . and dis-stress.

The presence of a limb length discrepancy usually is easily recognizable during gait by observing the following:

  • - Shoulder tilting to one side;
  • - Unequal arm swing;
  • - Pelvic tilt;
  • - Foot supinated on the short side and pronated on the long side;
  • - Ankle plantar-flexed on the short side; and/or
  • - Knee flexed on the long side.

The importance of limb length discrepancy cannot be ignored and may play a key role in lower limb and back pathologies. Integral parts of treating the condition are identification, comprehension of each individual's compensatory adaptations and their relationship to resultant symptomatology.

This article is from the Myokskeletal E-technique newsletter.
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References

  1. Blake RL, Ferguson H. Limb length discrepancy. JAPMA, 1992; pp. 33-8.