Wondering about the fitting process?
The foot is one of the most complex structures of the human body with 26 bones, 33 joints and over 100 ligaments, muscles and tendons. Until the late 1970’s, almost all prosthetic feet available were made of wood and foam. Expanding research and development of new prosthetic feet and material combinations push the boundaries of prosthetic design and improving the mobility and capabilities of amputees around the world.
The “blade” or “cheetah” feet seen in the Olympics are great examples of these engineering advancements. These carbon fiber “J” shaped feet are used primarily for running and are typically not used for everyday walking.
Many modern feet are built on the same principles of the “cheetah” running feet and are made with carbon fiber or fiberglass. These lightweight and sturdy materials provide a similar a “spring-like” effect, much like a diving board, and mimic the action of the ankle joint (dynamic response feet).
While there are thousands of prosthetic feet to choose from (and many more to come), there are several general categories. A K Level, or activity level, is chosen to determine the right foot for you based on your lifestyle needs.
The Solid Ankle Cushioned Heel or SACH foot is the most simple and inexpensive foot on the market today. Comprised of a wooden interior encapsulated with foam, this foot is lightweight and low maintenance. There is no active ankle joint, but the rubber “cushioned” heel of the foot compresses upon contact with the ground. SACH feet are best for patients with a lower activity levels.
Single axis feet have an ankle joint that enables the foot to tilt up and down. This movement quickly flattens the foot on the ground as soon as the heel contacts the ground, enhancing stability. This type of foot has more moving parts that require maintenance and can be slightly heavier. Single axis feet are best for patients with knee instability, low activity and slow walking speeds.
Multi-axial feet are able to move in a side-to-side motion. This is especially helpful for patients walking over uneven terrain or during quick directional movements. The multi-axial foot, shown without foot shell covering, displays one of the many styles of multi-axial feet, in which two shanks moving independently of each other to produce the side-to-side motion. Other types of multi-axial feet utilize different materials that are able to move and bend in different directions. Many modern feet incorporate multi-axial and dynamic response properties. Multi-axial feet are best for more active users.
Dynamic response feet, also known as “energy storing feet”, use the same principle as a diving board, releasing stored energy as the patient walks. The “spring” effect is only noticeable to the user and less energy or effort is required to use a dynamic response foot, allowing amputees to walk farther. As weight is placed on a dynamic response foot, carbon fiber or similar material absorbs the forces and as the foot is lifted off the floor, the foot propels the user forward (mimicking up and down movement of an ankle joint). Dynamic response feet are typically used for moderately to very active amputees who are able to walk at multiple speeds.
Vertical shock feet are designed to absorb the vertical movement during walking. Much like automobile shock absorbers that reduce the up and down movement of a car on the road, a prosthetic foot with vertical shock capabilities absorbs forces allowing for smoother walking. Vertical shock feet are slightly more expensive, heavier and best for patients with higher energy demands such as athletes and those that carry heavy loads.
The same “bionic” technology used in computer controlled knee and hand units has been adapted into foot and ankle systems. Benefits of powered ankle systems include a more normal gait pattern, ease of changing walking speeds and navigation of ramps and uneven terrain. Some microprocessor feet regulate the up and down movement of the ankle with hydraulic chambers while others can provide active propulsion or pushing off. Drawbacks of these systems include daily charging, increased cost and weight. P&O Care Practitioners are certified in the following microprocessor feet:
Hydraulic feet incorporate a hydraulic or pressurized chamber to control the up and down movement of the ankle during walking. Because of their ability to regulate the speed of ankle movement, hydraulic feet provide a significant amount of ankle motion to an amputee. Occasionally, the hydraulic chambers are controlled by an onboard microprocessor, while others do not. Hydraulic feet are excellent for those who walk up and down ramps/hills frequently and are great for bilateral patients. The increased cost and weight of hydraulic feet must also be considered. Hydraulic feet are available for both low and high activity users.
An adjustable heel height foot gives patients the ability to adjust the angle of the prosthetic foot to be able to wear up to a 2” heel safely. Many women and dancers choose this type of foot for its versatility. Check out this video of Amy Purdy, Former Dancing With the Stars Contestant, on the Freedom Innovations Runway Foot.
These feet are designed for activities other than daily walking. Skiing, swimming and running feet enable amputees to push the boundaries of physical activity.
Read more about our special use prostheses here.
We are proud providers of the following foot and ankle manufacturers.
Torsion adapters and shock absorbers are separate components that can be added to the top of almost any foot to provide rotation or shock absorption. Some feet already have torsion and vertical shock componentry incorporated into the design of the foot, but these added components can convert a foot to have torsion and shock properties. Many active users choose to add a torsion adapter to help with their golf swing and other activities in which rotation is required. Both torsion adapters and shock absorbers add additional length, weight and cost to a prosthesis.
Unlike the “J” shaped running feet, all everyday prosthetic feet feature some type foot shell, or protective covering. The foot shells keep the dirt and debris from the underlying components inside and have formed toes. The foam or plastic material fits around the inner of the foot and is typically only removed by the prosthetist for general maintenance. The foot shell resembles the user’s skin tone and many even have a split toe for sandals. You can even choose to paint your prosthetic toes too!