Biomechanics is the study of the mechanical principles of living organisms, particularly their movement and structure.[3]

People can easily identify with the title “Automotive Mechanic” yet they have great difficulty in understanding the concept of a “Biomechanical Specialist”. Quite simply, just as an “Automotive Mechanic understands and deals with the mechanics of a car a “biomechanical Specialist” understands and deals with the mechanics of the human body. While the logic of understanding the mechanics of the human body can be quite similar to understanding the mechanics of a car, one major difference is that a faulty mechanical problem with a car primarily hurts the pocket, while a faulty mechanical problem with the human body causes pain and often disability.

Let’s look at a couple of comparable instances .If a car has a flat tire, one side of the car becomes lower affecting the alignment and forward progression of the vehicle. Comparing the situation to the human body, if one limb is lower or shorter than its’ contralateral component a number of painful scenarios can follow

1. The longer limb spends more time on the ground causing increased forces (that are passed up the entire limb to the hip and lower back) and greater wear and tear on the body. This can create heel issues, knee issues, hip issues (and possible replacement), low back pain, trochanteric bursitis, Iliotibial Band problems, etc.

            2. The forefoot of the short limb experiences greater forces than the forefoot of the longer limb because the heel of the shorter limb does not have full contact with the ground exerting more pressure on the forefoot (sessamoiditis, metatarsalgia, fractures, etc)

The above scenario is easy to imagine, but what about the issues that aren’t so obvious (carburetor issues, spark plug malfunction, dirty filters, etc.) The human body comparison involves lines of force, angles of inclination, propulsive sequences, recruitment issues, and more. For example, by combining detailed measurements and computerized gait analysis, as a physician I can identify and treat 6 different kinds of shin splints within each limb, relieve the stress of trochanteric bursitis, Iliotibial Band Syndrome and Piriformis issues. These issues are secondary to faulty biomechanics (pathomechanics). To treat them we must address their causes. Treating them directly only offers temporary relief. In fact, direct treatment of these issues with steroids and pain relievers only masks the pain while the actual injury continues to get worse.

These issues can only improve by correcting biomechanical imbalances that cause them. Many of the imbalances are initiated in our propulsive sequence( the way we stand, walk and run and are directly related to the structural integrity of our lower extremities, starting with the foot, through which forces are passed upward to the superincumbent body.

Let me demonstrate by a simple example, the effect a small change in an angle at the level of the foot has on the superincumbent body. Place a pencil at a right angle to the ground (upright on the ground). Now lean the pencil just slightly toward the ground While at ground level you might have only moved 1/8th of an inch, look at how much more the top of the pencil moved. Now imagine the pencil a limb extending upwards 2 to 3 feet. INSERT DRAWINGS The top of the pencil could have easily moved 1 to 2 inches creating dramatic movement at the level of the hips.

Now lets apply the above scenario to the body in a couple of different ways and you will understand the importance of the mechanics of the body and their affect on joint motion and pain.

QUESTION: Why are many issues unilateral (one side of the body)? If the body were uniform both sides should be affected equally (Both hips, both knees, both legs). Usually, injuries are asymmetrical(right knee, left Achilles, right lower back, etc.). We think of our bodies as symmetrical (2, hands, 2 feet, 2 ears), but if we examine the similar parts of our body we realize they are considerably different from one another.

Look at your hands….facedifferences expand


Some simple self tests that can help identify causes of pain due to faulty mechanical relationships in the body.

**At the end of this paper I will explain in greater detail terms like Forefoot Valgus, Forefoot Varus, Genu Valgum, Genu Varum, etc.


TEST #1-Limb Length Discrepancies (LLD)


When one limb is longer than the other (sometimes as little as 1/8th of an inch it can play havoc on the human body. I have been using computerized gait analysis for 25 years and I am still amazed at some of the results. For example:

We spend more time on our longer limb.

The cumulative weight load of the longer limb is usually greater than the shorter limb.

Applying the above information I realized over the years thatLLDiscrepancies are responsible for non traumatic deterioration of both the hip and knee joints. Usually one hip starts to deteriorate causing pain and so the patient would then favor that hip and overuse the opposite hip which would then become painful and so one starts flipflopping between the hips until the degeneration becomes so bad that a hip replacement is needed. Unfortunately in many cases the new hip not only tends not to balance the hips but actually exacerbates the limb length discrepancy. (It is very difficult to take into consideration a multidtude of factors affecting the exact length of the nw hip in relation to the contralateral limb.

The same holds true for knee issues which are often complicated by abnormal relationships between the knees and within the knees. Genu Varum and Genu Valgum increases the force on opposite parts of the meniscus which are then exacerbated by the uneven weight bearing caused by the LLD.

As we move down the kinetic chain, one ankle receives more stress than its partner and issues like differing degress of rearfoot varus and rearfoot valgus cause a left rearfoot to endure stresses much greater than the right rearfoot.

It doesn’t end here, Sessamoiditis, a common forefoot issue is also victum of the LLD particularly in a foot with Forefoot Valgus.

While determining the exact LLD and differentiating between a functional LLD and a structural LLD (discussed later) one can often tell in a couple of minutes if a LLD exists..

Take a sticky note pad and peel off ¼” if paper. Take off your shoes and socks and place your feet together (heel to heel and toe to toe). Now(especially if you are a righty) place the wad of paper under your right heel (keeping your feet together).

Stand for 30-40 seconds.

Now step off the paper.

Then step back on it.

Did you notice a shifting of weight on your limbs and did you notice a change in the way your lower back felt –possibly more relaxed.

Do this a few more times and pay attention to your back (relaxing and getting tight) and pressure changes in your limbs.

If you notice changes (which are usually quite pronounced) then you have a LLD which can often be remedied by placing a lift (a wad of paper, a piece of cork or vinyl, etc.) in the heel of your shoe.

If the test is positive you should confirm your results with a healthcare physician (Orthopedic specialist, Chiropractor, Podiatrist). You might need a lesser or greater lift or if the issue is functional a chiropractic adjustment.

You will t least have a starting point for solving many lower back, hip knee and foot issues. 

Improving the body’s efficiency

Test #2 Forefoot test---same with the inner frft===outer frft   etc

Notice differences in their effect


 Garry Sherman, DPM, ABPOPPM, APMSB