Gait Cycle Basics: Part 4

Pronation as a shock absorber

Heel strike, a traumatic deceleration event with the transfer of weight from one extremity to the other, creates shock which must be attenuated. This is accomplished by 4 distinct mechanisms:

1. ankle plantar flexion at heelstrike, followed by eccentric contraction of the pretibial muscles to decelerate foot fall.

 

2. subtalar pronation. As the coefficient of friction between the calcaneus and the ground increases, the talus slides anterior on the calcaneus while plantar flexing, adducting and everting. This motion causes concomitant internal rotation of the lower leg. Both these actions cause a time delay, allowing force to be absorbed over a longer period of time.

 

3. knee flexion. This is a reaction to the heel rocker, forward motion of the tibia, and passive tension in the posterior compartment. It is slowed by eccentric contraction of the quadriceps

 

4. contralateral pelvic drop, which is decelerated by the ipsilateral hip abductors (primarily gluteus medius). This occurs as weight is suddenly dropped on the contralateral limb

 

The rockers and shock attenuation are dependent on the integrity of the joints involved, their associated ligaments and cartilage, the functionality of the musculature crossing them and their neuromuscular integrity along with appropriate cortical control of the actions. Being physical medicine practitioners, we understand that the anatomy and physiology cannot be separated and must consider these different components while evaluating the patient.

The Gait Guys….Yup, we ARE foot nerds….Hey, someone has to do it….

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Gait Cycle Basics: Part 3

As Promised: The Rockers…

According to Perry, progression of gait over the supporting foot depends on 3 functional rockers

heel rocker: the heel is the fulcrum as the foot rolls into plantar flexion. The pretibial muscles eccentrically contract to decelerate the foot drop and pull the tibia forward

 

ankle rocker: the ankle is the fulcrum and the tibia rolls forward due to forward momentum. The soleus eccentrically contracts to decelerate the forward progression of the tibia over the talus. Ankle and forefoot rocker can be compromised by imbalances in strength and length of the gastroc/soleus group and anterior compartment muscles.

 

forefoot rocker: tibial progression continues and the gastroc/soleus groups contract to decelerate the rate of forward limb movement. This, along with forward momentum, passive tension in the posterior compartment muscles, active contraction of the posterior compartment and windlass effect of the plantar fascia results in heel lift.

Now see if you can pick out the rockers in today’s video.

The Gait Guys… We are everywhere!!

Gait Cycle Basics: Part 2

Gait Cycle components

Let’s begin today with a typical walking gait cycle.

There are 2 phases: stance and swing. It comprises approximately 62% of the gait cycle. Inman and Scranton use the following classification:

 

Heel strike: when the heel hits the ground

Full forefoot load: weight is transferred anteriorly to the forefoot

Heel lift: when the heel begins lifting off the ground

Toe off: the beginning of propulsion

 

They further divide this into a contact period (heel strike to full forefoot load), a midstance period (from full forefoot load to heel lift) and a propulsive period (from heel lift through toe off)

 

Jaqueline Perry, the Matriarch of gait, uses a slightly more descriptive classification which we prefer:

 

Initial contact: when the foot 1st touches the floor

Loading response: weight bearing on the loaded extremity from initial contact and continues until the opposite foot is lifted for swing

Midstance: the 1st ½ of single limb support, beginning when the opposite foot is lifted until weight is over the forefoot

Terminal stance: begins with heel rise and continues until the opposite foot strikes the ground

Pre swing: when initial contact of the opposite extremity begins and toes off ends

She also describes 3 tasks to be performed during a gait cycle: weight acceptance (the limb is able to bear weight), single limb support (when weight is supported by one limb with the other in swing phase), and swing limb advancement (moving the opposite limb through space to become the next stance phase leg.

The question is, how do we adequately progress over the stance phase leg? Stay tuned to our next post for a primer on the 3 rockers….

The Gait Guys…Promoting gait literacy and understanding for the clinician and the consumer.

This week we will focus on the basics of gait and the gait cycle in our attempt to assist in gait literacy

Gait Cycle Basics: Part 1

Steps and strides….

What does the gait cycle that have to do with therapy or rehabilitation? Well, most people walk at some point in the day, and most have walked into your office. If people can’t carry the changes you made on the table and incorporate it into walking, then what you do will have limited effectiveness. Thus, the need for understanding the gait cycle as it relates to rehabilitation or how it can give you clues to the biomechanical faults present. An example is a loss of functional hip extension and chronic LBP/ SI dysfunction. This could be due to a myriad of reasons, from weak glutes, loss of ankle dorsiflexion, or even a dysfunctional shoulder. Understanding how these seemingly unrelated body parts integrate into the kinetic chain, especially while moving upright through the gravitational plane.

 

One gait cycle consists of the events from heel strike to heel strike on one side. A step length is the distance traveled from one heel strike to the next (on the opposite side). Comparing right to left step lengths can give the evaluator insight into the symmetry of the gait.  Differences in step length, on the simplest level, should cause the individual to deviate consistently from a straight line (technically it should cause the individual to eventually walk in a large circle!).  Often, compensations occur functionally in the lower kinetic chain to compensate for the differences in step length to ensure that you walk in a straight line.  It is these longstanding complex compensations that are the generators of many of our patient’s complaints.

 

A stride length is the distance from heel strike to heel strike on the ipsilateral side (the distance covered in one gait cycle.  Step width, or base of gait, is the lateral distance between the heel centers of two consecutive foot contacts (this typically measures 6-10 cm).  Foot progression angle is the angle of deviation of the long axis of the foot from the line of progression (typically 7-10 degrees). Çhanges in the progression angle can be due to both congenital (torsions, versions) as well as developmental reasons.

Next time we will take a closer look at the gait cycle itself. Yup, we are still…The Gait Guys

special thanks to Dr. Tom Michaud, who has allowed us to use these images in our book

The pedograph as a window to the gait cycle

Have you ever studied footprints on the beach or looked at the print left by a wet foot when you get out of the water? These are some of the most primitive types of pedographs.

The pedograph, 1st described by Harris and Beath in 1947 is a rubber mat surface with multiple protruding, small grid lines on one side, which, when covered with ink, imprints an underlying sheet of paper when weight (usually a foot) passes over it. Relative plantar pressures are indicated by the size and density of the inked area, creating a “footprint” reflecting passages of force through the foot at that instance in time.  They have fallen into and out of usage over the years, often discarded for more expensive technology such as pedobarographs, individual pressure sensors, and pressure sensitive mats, which have computer interfaces and can provide many useful measurements and calculations to assist the clinician with rendering a diagnosis. These systems, though more precise in some ways (provided a controlled, reproducible testing procedure) are often thousands of dollars, require a computer and the necessary skills, and have a substantial learning curve. 

The pedograph in contrast is simplistic, inexpensive, and reliable and only requires that the user have an intact visual pathway and cerebral cortex and knowledge of the events occurring in the gait cycle. With some practice and a good knowledge base, the subtle nuances detected by the sensitive pedograph (nuances that can be undetected with high end computer driven plantar pressure devices) can offer information critical to a precise diagnosis and give solid clues to gait flaws and compensations.  With minimal training using a pedograph, reproducible “prints” can be produced for analysis, in light of your findings clinically. They also make wonderful educational tools for your patients and clients!

An essential part of a comprehensive patient evaluation should include examination of the entire kinetic chain both in a static and dynamic fashion. Often what you see statically is either directly translated to or compensated for in the dynamic evaluation. (It is important to note that many of the available foot scan units available from orthotic companies scan a patient in a static standing position and give little information on how the feet and lower limb dynamically engage the ground during movement.) The pedograph is a useful visual tool representing a 2 dimensional image of tridimensional motion, and you are seeing the end product and compensation (or lack thereof) of the individuals mechanics at that point in time. Because of the specificity of what you are seeing refers to a particular point in time, technique and reproducibility are of paramount importance. Prints should be performed several times to insure what you are looking at is what you are looking at, and not movement artifact, because of the way the patient stepped on to or off of the mat.

With a pedograph, seeing is believing. When you have objective data about how an individual moves through space and how their joints and motor system help them to accomplish that, you have a better appreciation for the type or form of therapy which may be most appropriate. In the hands of a skilled clinician, seeing abnormal plantar pressures tells you where the biomechanical fault lies, and thus where manipulation may be appropriate, which muscles need strengthening and where neuromotor coordination is lacking and gait rehabilitation is needed.  

excerpted from the 1st edition of our Book “Pedographs and Gait Analysis: Clinical Pearls and Case Studies” Trafford Publishing

How do I know if my orthotic is working?

Foot orthotics are easy, no? You get casted, it gets built, you put it in your shoe and you’re good to go, right? Wrong!

Orthotics or “Orthotic Therapy” as we call it is an ongoing process. If an orthotic is doing it’s job, your foot should change (for the better) and your prescription should become less. and less….Until you no longer need them… At least in an ideal world.

Remember, orthotics are designed to help you adapt to your environment better. Unlike a footbed, they should change the biomechanical function of your foot. A lot should go into getting fit for an orthotic, otherwise they can actually cause some of the problems they are purported to fix!

First of all, there should be a history of you and whatever is going on, with an inventory of all your past injuries. Sometimes there is a pattern that can be recognized and gives your provider clues as to what may be going on with you.

Next you should have a thorough examination of your lower kinetic chain, including the feet, ankles, knees, hips and low back. This should include range of motion, muscle strength, muscle recruitment patterns and joint function, along with reflexes, sensation and balance or proprioception. This gives us a benchmark and defines weaknesses and strengths.

Now there should be an analysis of your gait, preferably with stop motion video which allows us to slow down movements and assess subtle abnormalities that may not be visible during normal speeds of movement. If you are there for cycling orthotics, then a video of your stroke pattern is made. Sometimes, footage of your skiing technique can be helpful as well.

At this point, it should be obvious to both you and your orthotic provider whether or not an orthotic is needed. If so, a non weight bearing cast in terminal stance phase (This is a specific position of your ankle and foot) should be performed. This is usually followed by the prescription of appropriate stretches and exercises, specific to your condition. Shoe recommendations should also be given, since different foot types require different footwear characteristics. This will be good news for the ladies who like many shoes. Most guys just want the pain to stop and won’t care what they look like, as long as they are not pink!

Now you have an idea of what goes into (or should go into) building the perfect orthotic for you. Ask lots of questions of whoever is building them for you and make sure they are answered to your satisfaction. They should be a stepping stone to your recovery and  not a crutch for you to depend on. 

Telling it like it is, we are… The Gait Guys