Everything You Need to Know about Prosthetic Feet

This is one of the “OG” or originals of prosthetic feet! It has a neoprene/urethane shell molded over a wooden keel and rubber heel to simulate planterflexion. The foot provides movement when it bends or flexes around the rubber areas when the amputee puts weight into it. For example, when the person places the heel on the ground, the heel will compress and allow the foot to plantarflex to the ground. Then as the person rolls through the foot, it will bend at the toes where the rubber meets the wooden keel. Now, there IS a SACH foot on the market that has a flexible keel that will deform under load (when the weight goes into the foot) and allows for a little shock absorption and a small assist when the amputee rolls over the foot and pushes off. For many decades, the SACH foot was the most commonly used foot.

This foot is another “OG” and is one step (pun intended) above the SACH foot. It has a single axis and allows for plantarflexion and dorsiflexion (moving your ankle up and down motion). This is a very simple foot and is typically for lower level mobility. One of its advantages is that it offers good knee stability especially to my above knee amputees when they put full body weight into the socket during midstance in gait. There are rubber bumpers inside the foot that provide cushion and will determine how much movement is allowed. This is also a fantastic option for a pool/beach foot as manufacturers make this low cost and in some cases, water resistant! This foot is meant for those who are low activity but want a little more movement than the SACH foot.

Now we’re getting a little more “fancy!” This foot allows for movement in plantarflexion/dorsiflexion as well as inversion and eversion (side to side ankle motion) and a little rotation (or a lot depending on the manufacturer) to add some spice! This foot provides for a lot more mobility which in turn, provides a little less stability (when compared to the SACH and Single Axis feet). Keeping in mind, these movements occur because of the user pushing down with their body weight to move in these directions. The foot does not move in these directions by itself (like a robot). With this increase in available motion, you get better absorption of stress (compared to a Single Axis foot) which in turn, cuts down on the wear and tear of your skin. While the SACH and Single Axis feet give you a sturdy foundation, the Multi Axial foot is designed for folks who want more movement with their step and also have the balance and coordination to control the movement to their advantage.

Now we’re cooking with grease! The Dynamic Response foot is typically made from carbon fiber materials that will deform under a load (when you put your weight into it) and will return to its original shape when off loaded (when you roll off the foot). So while this technically is not an energy storing foot, it does provide energy return as it is returning to its original form. (Yeah, it took me a minute as well to understand the difference!) These feet will have a nifty “J” shape design at the ankle.

But wait, there’s more! Many folks (myself included) will talk about an ESAR in the same way as a Dynamic Response Foot. This is because they are very similar in many ways! They both give energy to the user during the roll over (loading response/midstance/heel off) stages of gait, they just do it in a slightly different manner.

Think of the the ESAR foot as a pogo stick (or like Tigger from Winnie the Pooh). When you put your weight into this foot as you take a step, the foot stores that potential energy (hello high school physics!) and then returns that energy to you when you are pushing off with that foot. More precisely, it stores that energy in the keel when you roll over your weight onto it (during loading response and mid-stance for those of you smarties who have listened to my gait talk). It’s what gives “pep to your step!” It also gives a more normal sense of range of motion and symmetry to the gait pattern. In certain feet they have a split toe design component added to give you some of that inversion and eversion capabilities. Some are even designed to allow for decreased impact forces on the sound limb. This is for moderate to active individuals who put their foot through the gauntlet.

*Please refer to the Dynamic Response Foot for the advantages/disadvantages of the ESAR-told you they were similar!

As the name suggests, this foot has a hydraulic component which helps passively control the plantarflexion and dorsiflexion.  It absorbs the energy that is then dissipated as heat into the hydraulic fluid.  The hydraulic unit allows for more contact on the ground therefore increasing your stability and taking it to another level.  As a bonus, it also helps reduce socket pressure.  

This foot is great for folks who walk a lot on uneven terrain or who have to negotiate their fair share of slopes and ramps.  My patients and viewers who use a Hydraulic foot state they feel more “connected” to the ground.  This foot is recommended for moderately active to active individuals.

Now this is a classification I made up myself about 10 years ago when I started seeing an explosion of feet and amazing technology on the market. Many manufacturers now have feet that combine the above classification. If a Dynamic Response foot and a Multi Axial foot had a baby, it would be this foot!

Read this friendly warning, if you ask your prosthetist for a Hybrid foot, they will look at you with a puzzled expression because remember, this is a term I created! If you feel that both the Dynamic Response foot and Multi Axial foot have features that would benefit you, then ask your prosthetist which feet on the market have this particular combination.

Much like a microprocessor knee, an MP foot is a foot that at its base, is a Hydraulic foot but also has a microprocessor (computer) inside. This microprocessor uses sensors to analyze the environment to determine how much the friction in the foot needs to be adjusted. Sounds complicated? It is certainly a more sophisticated foot and higher tech and is meant to take the “guesswork” out of walking for the individual.

There are other MP feet out on the market that feature multi axial components as well as feet that use propulsion in their MP technology. It is important to understand that while a Microprocessor foot means it is controlled by sensors and a computer inside the foot, the base of the foot itself is where you want to ask deeper questions (is it Hydraulic? Multi axial? Propulsion? Etc.)

Another friendly warning, many of my patients and viewers have had (literally) life changing experiences by switching to a MP foot. Please be aware that because of the delicate technology, you cannot “beat” this foot up and the cost if it is damaged is something you need to take into account. It also tends to be a heavier foot which will not be a problem as long as you make sure you and your prosthetist are diligent about having good suspension and a pristine fit with your socket! (Psst! Here is a show where I explain all the different suspension systems you can watch after you read this!)

I won’t lie, I get a big ole smile on my face when I talk about running blades. This is partly because I am a runner girl and teaching amputees how to run is my second favorite thing to do (teaching amputees how to walk again is my first!). This is another industry that has boomed in recent years and we are starting to see advances even in legislature that are requiring insurance to pay for them!

You guessed it, a friendly warning! Running is not for everyone and that is ok! Here’s what I mean. I believe most amputees who walk with a prosthesis would benefit from learning some of the basics of running. The purpose being to utilize this skill during an emergency such as getting to the other side of a crosswalk before the cars race through, or perhaps outpacing your spouse who wants that last piece of pie in the fridge as much as you do!

Running is a pretty harsh sport on the human body (ask me how I know) and should be done with a mind to training properly, receiving instruction from a licensed professional, and a commitment to minimizing injury with a proper routine that includes strengthening. Ok, Physical Therapist Soapbox over. Back to the running blade…

Even if you are a prime candidate for running, I would encourage you to ask your prosthetist if you can use your current prosthetic foot to begin learning.

One of my favorite running buddies, Daymon, used his daily prosthetic foot to learn the basics of running mechanics. This was of course done with the blessing of his prosthetist! Once he mastered a solid running gait, he was then able to look into trialing different prosthetic running blades. Because he had learned the mechanics of running, he was able to appreciate the differences and what would feel best for his running gait. I am so glad he took this approach because blades can be an expensive investment and much like your daily walking foot, you don’t want to get the wrong one!

Psst again! You can watch some of my first running sessions with Daymon NEED LINK(here)!

This is the unsung hero of prosthetic feet (in my humble opinion)! This foot is typically a rectangular shape and kind of looks like a goat’s hoof-seriously! It is very simple design but has many applications. First and foremost, the Stubbie is a great starter foot for my bilateral above the knee amputees.

Here’s why.

The Stubbie can attach directly to the bottom of a socket without a pylon (the long metal pole that connects the socket to the foot). This allows my bilateral AK’s to start their standing and walking rehab much lower to the ground. They can build strength and confidence while low to the ground and then progress to full length prosthetic limbs with knees when they are ready.

Looking to gain an advantage for rock climbing? This is where the Stubbie foot can give you an edge (Cosi, enough with the bad puns). You can swap out your prosthetic foot for a Stubbie and have a much better grip on a tiny rock!

I also really love this foot for the beach, pool, and shower. It is an inexpensive and hardy option for water lovers. You may have noticed I have not mentioned any particular foot by their manufacturer but here is where I will break the 4th wall and say that I absolutely LOVE the Sidekicks Stubbie by College Park Industries. This particular Stubbie not only has a beautiful tread on the bottom to really help you grip the ground but also has a multi axial component!