Westside Wellness: Los Angeles

The Gait Mechanism or Walking Mechanism

The human gait is controlled almost exclusively by the foot. There are nerve sensors in the foot and ankle joints that tell our brain where we are in three dimensional space. That either sounds very simple to you or completely overwhelming depending on your point of view. This makes stability of the foot extremely important for all structures of the body. In our office we utilize exercise rehab and orthotics to give maximum stability to the foot for a normal gait mechanism. The more active you are or the more you stand on your feet the more likely you are to need orthotics. That being said it is a fairly genetic trait to have foot dysfunction. So ask your parents which had problems with their feet and you can find where you got it from. That's the simple explanation. Below is the more technical and complicated information so enjoy.

Orthotics - Devices placed in the shoes to control foot motion.

Orthotics can be made in many different materials. But I insist on making the molds for the orthotics non weight bearing. I agree with the majority of thinkers on this issue. If you take a mold of a foot while weight bearing you get a mold of a deformed foot. So you simply make an accommodative appliance which never addresses correction. Whether we use leather, plastic or any material in between the goal is stability. All aspects of the foot should be taken into consideration, not just the longitudinal arch.

Mechanism of Gait

• Bipedal gait is a learned activity; each person has an idiosyncratic gait. All other animals locomote like all of their species.
• Gait cycle: from heal strike on one foot to heal strike on the same foot.
• (1) Stance Phase : when one is supporting themselves = heal strike (when heal hits the ground), foot strike (when heal of the foot is on the ground), toe off (when up on toe and about to kick off)
• (2) Swing Phase : when one's leg is swinging = early swing, late swing
• Walking is about getting one's foot behind one's center of gravity
• for quadruped this is always true so anything that generates friction in rear direction causes forward motion
• for biped we have to get our center of mass (pelvis in front of S2) out in front of our feet, which is inefficient.
  • this requires that we balance over our hip because it is a frictionless ball-n-socket joint.
  • Plumb line from Center of mass would run in front of knees and ankles but slightly behind hip
  • So we should pitch back on hips and buckle forward in the knees and ankles looking like a concertina
  • Ileofemoral ligament (large) [from AIIS to inner trochanteric line on femur] stops us from pitching back
  • Knees don't buckle in the wrong direction because of the anterior cruciates and collateral ligaments
  • Ankle has no ligament due to need for motion there; when rocking forward, center of mass goes in front of the feet, so plantar flexors are fired to push us back. This is how we stand.
• Walking bipedally is done one leg at a time. We are the only animal that can stand on one leg because the abductors: Gluteus Medius, Minimus and Tensor fascilata contract with every step we take and hold us up.
• The reason that women have much greater failure of joints is that they have wider hips due to the birth canal. Note that the wider the hip the greater the horizontal component of the quad-vector, which works in opposition to the fibers of fascia medialis (which fire late in extension cycle to hold the patella in place). This leads to stress on knee
• In the hip, the abductors run from the greater trochanter to the pelvis. The center of rotation is in the middle of the femoral head which acts as a fulcrum between the center of mass and the force of abductors. A wider hip extends the moment arm between the center of mass and the fulcrum of the female pelvis. Therefore greater abductor force is required to balance to same mass thus increasing the joint reaction force considerably.

Muscles of Gait cycle

• Acceleration of thigh is the action of the Iliopsoas and Rectus femoris. Rectus femoris is important because sprinters can tear this off the anterior inferior spine where it originates- comes off easily due to cartilaginous apophysis attachment.
• Deceleration is accomplished by hamstrings which come across the hip joint and contract eccentrically (elongating).
  • So hamstrings are pulled by athletes who decelerate quickly or kick Þ pulling the muscle off the ischial tuberosity.
• Heal Strike fires the Dorsiflexors (anterior tibial group:Tibialis anterior etc., deep fibular n. ) eccentrically contract and lower the foot to the ground. Quadriceps eccentrically contract to absorb energy as knee goes into 5 o flexion; this prevents the knee from buckling
• Foot Strike : abductors contract to hold body up. As center of mass moves forward the Plantar flexors (triceps surae: gastrocnemius, soleus, and plantaris ) contract to push body ahead.
• Toe off : Quadriceps concentrically contract to help the plantar-flexors push body ahead by elongating lower limb.

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