The prosthetic foot is one of the basic components of a lower limb prosthesis. Whether the amputation is above-knee or below-knee, the overall performance of the prosthesis is largely influenced by the characteristics of the prosthetic foot. The foot forms the foundation on which daily functions such as standing, walking and moving are based.
How is a prosthetic foot designed?
Prosthetic foot design is a complex process, as it aims to reproduce the natural movement of the human foot and ankle. Ideally, a prosthetic foot should combine the following characteristics:
- Lightness: Because the weight of the foot is added to the rest of the prosthesis, it is expected to be as light as possible.
- Durability: It should be strong enough to withstand the high forces and torsion that occur during walking and running.
- Suitable size: It should be small enough to fit inside a cosmetic foot shell and a shoe.
Modern prosthetic feet are usually fixed inside a cosmetic shell. This shell gives the foot a natural anatomical appearance and allows it to fit comfortably inside ordinary shoes.
Energy-storing carbon-fiber feet
Energy-storing dynamic carbon-fiber feet are designed to store and return energy during walking. The carbon fiber behaves like a spring: it compresses when weight is applied, and then, as the foot rolls over the toe, it releases the stored energy, adding forward propulsion to the step.
Some prosthetic feet have two springs, one in the heel and the other in the forefoot. This design supports the flexibility and control needed when walking at different speeds, running, walking uphill or going down stairs. You can also look at the carbon-fiber foot types for prosthetic legs, which vary according to activity level; in general, the longer the spring, the more energy can be stored and the more responsive the foot becomes.
Activity levels
The activity level reflects how the person uses their prosthesis in daily life and guides the selection of suitable components. Four levels are commonly defined:
- Level 1: Use of the prosthesis on level ground over short distances and for transfers; walking time and distance are limited.
- Level 2: Limited walking indoors and outdoors, with the ability to overcome low obstacles such as a curb or a single step.
- Level 3: Users who can walk at varying speeds, overcome most environmental obstacles and move without restriction.
- Level 4: Users with no limit on duration or distance, who can meet high functional demands and therefore high shock and stress.
Criteria considered when choosing the right foot
Determining the suitable prosthetic foot is an individual process carried out in line with the specialist physician's assessment and prescription, with the biomechanical knowledge of the prosthetics and orthotics specialist (prosthetist). The following factors are taken into account in the selection:
- Amputation level: In above-knee amputations, the type of knee joint affects the selection; below the knee, the length and condition of the residual limb do.
- Activity level: Daily loads and level of mobility are decisive.
- Body weight: The foot is sized and certified to carry the weight safely.
- Build height: The distance between the residual limb and the ground determines which feet will physically fit.
- Foot size and personal factors: Lifestyle, goals and preferences are included in the selection.
Frequently asked topics
Thanks to a cosmetic shell, prosthetic feet can usually be used with ordinary shoes; however, it is important that the heel height of the shoe matches the heel height to which the foot is calibrated. Although many feet are designed to be resistant to water and humid environments, the water resistance classification varies by product. Trial fittings can be carried out to understand how different feet feel in daily life. For athletic and recreational use, there are specially designed feet considered within the scope of sports prostheses and components.
This content is for informational purposes; you should consult your physician for diagnosis and treatment.
