The Reverse Double Whammy Leg Check

Let's talk leg checking. The patient may have come in with anything from mild low back pain to projectile vomiting, but from the chiropractor's point of view, it just may be that the true cause of the dis-ease has left behind a smoking gun ... a functional short leg! The doctor stares intently at the patient's feet, incognizant of virtually all other sensory stimuli, at least momentarily excluding from the differential diagnosis all but that most ancient of questions: which is the short leg?

But wait, something is wrong! How's a doctor supposed to make that simple determination, the side of the short leg, when the patient's feet are out there flopping around like fish out of water? One foot is dorsiflexed, the other plantarflexed; one may be laterally rotated, perhaps inverted as well. Innate intelligence must have been feeling kind of mischievous the day the leg check was invented, because she (or he) drowned that one datum screaming for detection, the dichotomously defined side of the short leg, in a sea of noise, submerging the signal to noise ratio in a flood of other degrees of freedom. Five of them.

A foot, after all, may rotate and translate simultaneously around any of the body's three axes, thus enjoying a total of six degrees of freedom. Of the three translatory motions, in the absence of ankle or foot fracture-dislocations, only longitudinal displacement of the foot on the Y axis -- indeed, the functional short leg phenomenon -- seems clinically realistic. Even in that case, it occurs not for any local foot-related reason, but because the entire lower extremity is displaced cephalad relative to the other. As for the three rotational motions, all occur: dorsiflexion/plantarflexion around the X axis; internal/external rotation ("foot flare") around the Y axis; and inversion/eversion (perhaps supination/pronation) around the Z axis.

So the doctor, intent upon discerning a possible Y axis foot translation amidst a sea of uncertainty, grabs the feet, straightens them out, pushes up a little, and primarily tries to make them stay put! Unfortunately, one can not remove three concurrent foot rotations with clinical impunity. Grabbing, straightening, and pushing the feet obviously alters where they are, and how they are. It will not be easy to prove that the doctor has detected anything other than what he alone has created, that the short leg he has worked so hard to discern is anything other than an artifact of his own impatience with undesirable degrees of freedom. Ideally speaking, you don't want your measuring device to change the thing it is measuring, or at least, if this is not possible, you want to change things in a known way. No luck here. When the doctor grabs the feet and pushes on them, as so many technique manuals recommend, there's no guarantee that the cephalad pressures are symmetrically applied, nor that leg length inequality detected in this manner is interpretable.

It is not necessary to do leg checks this way. I don't know who was the first chiropractor to fetishize Y axis translation at the expense of all other elements of foot posture, but it was a great mistake. This reductionist move not only obliterated all kinds of important clinical evidence, but made it practically impossible to see the leg check for what it is: one aspect among others of a non-weightbearing postural examination. There is no a priori reason to suppose that all the other foot postural evidence we suppress in a desperate attempt to discern Y axis displacement is any less important than the one irrationally vaunted datum.

Imagine if we did standing postural examinations in the same way; that, for argument's sake, amidst a great cornucopia of positional asymmetries, we simply demanded to know which hand hung lower. Then we would have to make sure the shoulders were not rotated, that the elbows, wrists, and fingers were extended, and possibly that the torso was facing directly forward. By the time we were done "correcting" all these confounding postural factors, we would no longer remember that our very purpose in examining the patient was to detect postural asymmetry.

The Sign of the "PI Foot"

So let's get back to those feet, those fish out of water, "misaligned" as they see fit on three axes of rotation and one of translation. Asymmetric foot postures must result from asymmetric function and displacement of the lower extremities, which in turn relates to asymmetric neuromusculoskeletal function of more cephalad structures. For reasons I develop elsewhere,¹ I think asymmetric foot postures principally reflect pelvic torsion. Indeed, the foot findings in the prone examination are so distinctive that they warrant the designation "PI foot." Three of the findings have to do with foot posture, and the fourth with asymmetric left/right shoe wear.

The four signs on the side of the PI ilium are: inversion (i.e., supination); external rotation; leg shortening; and accelerated posterolateral heel wear. The signs are much more obvious if passive range-of-motion is checked: in other words, if the examiner takes external rotation and inversion to the end-points, left and right, and compares the range-of-motion. This also applies to longitudinal displacement, or cephalad loading, of the lower extremities. This is preferred to simply observing the passive foot carriage.

• Inversion/supination

It may seem paradoxical that the non-weightbearing foot is relatively supinated on the side of the posteriorly rotated innominate bone, which (again, for reasons I develop elsewhere) is accompanied by ipsilateral pronation in the standing position. During ambulation, the neuromuscular control system attempts to compensate for the decreased height of the longitudinal arch by over-activating the tibialis anterior. This hyperactivity of the tibialis anterior may be so marked that it wears out a groove in the anterior medial plantar portion of the navicular bone in the line of its tendon. "Apparently the bone effects were caused by long continued over activity of the tibialis anticus muscle tendon unit. This was the result of a maintained unconscious effort on the part of the patient to lift up the inner border of the foot in walking or standing."²

Whether or not these muscles are able to favorably affect the dynamic function of the foot during locomotion, in the standing position they are futile: the foot remains pronated. Nonetheless, in the prone position the hypertonic contracture of the tibialis anterior is effective and the foot is inverted. The inversion is caused by tibialis anterior hyperactivity, sustained as part of an unconscious attempt to maintain the integrity of the medial arch in walking and in standing.

• External rotation/foot flare

The external rotation is caused by piriformis hyperactivity, the result of an attempt to maintain postural homeostasis, given sacral apex deviation toward the anteriorly rotated innominate bone. The piriformis muscle, an important lateral rotator of the leg, originates from three lips on the anterior side of the sacral border, the margin of the greater sciatic foramen, and the sacrotuberous ligament. It passes through the sciatic foramen to insert on the superior border of the greater trochanter. In Figure 2, adapted from Hildebrandt,³ the right piriformis muscle will become hypertonic in a vain attempt to pull over the sacral apex which has subluxated away from the contralateral inferior sacral base. Although the sacral apex deviation is fairly well locked in by the contralateral lowering of the sacral base, the piriformis winds up effectively laterally rotating the right leg.

• Leg shortening

The "short leg" in the traditional sense of the term is obviously worth its own article. I have had reason to believe it is the consequence of ipsilateral suprapelvic muscular hyperactivity.⁴ More recently I have been pursuing other lines of evidence in the laboratory using specialized equipment optimized for kinetically amplified detection of leg responsiveness to clinical interventions.^5,6

The sacrospinalis and quadratus lumborum muscles are hypertonic on the PI ilium side, but futile in their anti-gravitational attempt to pull up the pelvis and the sacral base by their bootstraps in the standing position. However, this futility becomes triumphant as soon as the patient is placed in the prone or supine position. These muscles are no longer trying to raise the pelvis against gravity, but only against the resistance afforded by the friction of the table exerted upon the recumbent patient. As a general rule, they succeed in laterally flexing the pelvis on the lumbar spine, raising the hip.

The more traditional explanation, the one which has a posteroinferior swing of the PSIS hoisting up the hip, would luxate the symphysis pubis. Usually, the shortening effect is either evident enough to see without touching the feet, or too subtle to be clinically significant. Any lingering doubts may be dispelled with some serious cephalad pressure, at a loading level well beyond what technique people tend to recommend. Under such loading conditions, what the leg check really checks is the motility of the lumbopelvis -- pelvic lateral deviation, lumbar bending, hip rotation, etc. -- in response to pressures applied through the lower extremities. This type of leg checking, if not all checking that involves pushing on the legs, is in reality a form of motion palpation.

• Accelerated posterolateral heel wear

It will also be noted that more often than not the lateral posterior aspect of the heel of the shoe is more worn down than its contralateral counterpart, having to do with the fact that the subject in effect attempts to walk more on the edge of his foot on the side of the posterior innominate bone. Heel strike always occurs, of course, with the foot in supination -- it's a question of the time spent in this position. The lateral heel wear results from walking on the edge of the foot, and remaining for a longer time in the heel strike phase of locomotion, resulting in greater abrasion.

[The only axis of rotation for the foot not herein addressed is the X axis, about which occurs dorsiflexion and plantarflexion. I am not sure that I have noted any particular tendency, probably because tibialis anterior and posterior are both hypertonic, "trying" (please forgive the teleology) to lift the pronated foot. Both are supinators, but tibialis anterior is a dorsiflexor and tibialis posterior a plantarflexor. This seems like a wash in that direction, although my rough impression is that plantarflexion usually dominates.]

A Leg Check at a Glance

So, for me, the "leg check" is a glance at the feet from several feet away. I don't have to touch the feet. I think that asymmetric foot postures reflect lower extremity responses to suprapelvic asymmetries, such as the PI ilium lumbopelvic distortion syndrome. When all four components of the PI foot are there, I'm very comfortable making the call. When there are inconsistent findings, such as shortening on one side and lateral rotation on the other, I am less comfortable. In murky waters such as these I sometimes find anatomical leg length inequality, or perhaps what Logan would have called a "non-basic distortion."⁷ I suppose leg length inequality in some cases could reflect lower extremity responses to supra-suprapelvic asymmetries, such as atlas subluxation, but I have no analysis to offer up at this time. Apart from the diagnostic information contained in foot posture analysis in particular, and non-weightbearing postural assessment in general, I am especially interested in leg responsiveness to different loading conditions, including not only the cephalad forces applied in the traditional leg check, but distractive forces. Why not pull on the legs to see which is or becomes the long leg? More to come on this reverse double whammy kind of leg checking.

References

1. Cooperstein R. Chiropraxis. Oakland, CA: Self-published, 1994.
2. Kopell, Thompson. Peripheral Entrapment Neuropathies.
3. Hildebrandt RW. Chiropractic Spinography. (2nd ed.) Baltimore: Williams & Wilkins, 1985.
4. Cooperstein R. Functional leg length inequality: geometric analysis and an alternative muscular model. 8th Annual Conference on Research and Education. Monterey, California, 1993:202-203.
5. Jansen RD, Cooperstein R. Measurement of soft tissue strain in response to consecutively increased compressive and distractive loads on a friction-reduced test bed. Journal of Manipulative and Physiological Therapeutics; in press.
6. Cooperstein R, Jansen P. Technology description: The friction-reduced segmented table. Chiropractic Technique 1996;8(3):107-111.
7. Logan HB. Textbook of Logan Basic Methods. St. Louis, Missouri: unknown, 1950. (Logan VF, Murray FM, eds.)

Robert Cooperstein, MA, DC
San Jose, California