Case Study: Overlay vs. Prosthetic Socks for Lower Limb Amputees
Quick answer
In this case study, transtibial amputees rated the Overlay higher than traditional prosthetic ply socks for comfort, socket fit, cushioning, and ease of use. They also reported lower pain levels while using the Overlay.
The Overlay is an adjustable prosthetic device designed to help lower-limb amputees respond to daily residual-limb volume changes and fine-tune their socket fit.
Why does prosthetic socket fit change?
A residual limb can change volume throughout the day because of activity, fluid shifts, temperature, time spent sitting or standing, diet, hydration, and other factors.
When limb volume decreases, the prosthetic socket may begin to feel loose. This can contribute to movement inside the socket, reduced stability, discomfort, pressure concentration, or the need to add prosthetic socks.
When limb volume increases, the socket may feel tighter and less comfortable.
Managing these changes is an important part of daily prosthetic care.
What are prosthetic ply socks?
Prosthetic ply socks are worn inside the socket to compensate for changes in residual-limb volume.
Users may add or remove different sock thicknesses throughout the day to adjust socket fit. Although this method is widely used, it may require the user to stop, remove the prosthesis, test different ply combinations, and repeat the process until the fit feels appropriate.
What is the Overlay?
The Overlay by Ethnocare is an adjustable prosthetic volume-management solution worn over the prosthetic liner.
It combines a textile sleeve with an integrated pneumatic system. By adding or releasing air, the user can make small adjustments to the volume inside the socket.
The Overlay is designed to:
- Help manage daily residual-limb volume variation
- Support socket fit
- Provide additional cushioning
- Reduce reliance on repeated prosthetic sock changes
- Allow users to adjust their fit throughout the day
The Overlay is not simply another prosthetic sock. It is an adjustable air-based system intended to provide more precise control over socket fit.
How was the case study conducted?
The internal study initially included 27 transtibial amputees who regularly used definitive prostheses and prosthetic ply socks.
Participants used both the Overlay and traditional ply socks in a crossover format. The order was randomized, and each solution was used during regular daily activities for at least two weeks.
Four participants were excluded because of study completion, comprehension, compatibility, or adaptation-related challenges, leaving 23 completed surveys for the final analysis.
Participants rated both solutions for:
- Comfort
- Fit inside the socket
- Cushioning
- Pain
- Ease of use
The study used self-reported rating scales from 1 to 10.
Overlay vs. prosthetic socks: results
1. Comfort
Participants rated comfort at:
- Overlay: 8.61
- Ply socks: 6.43
Participants therefore reported greater comfort while using the Overlay.
The Overlay ratings also showed less variability, suggesting a more consistent reported experience among the users included in the analysis.
2. Fit inside the prosthetic socket
Participants rated socket fit at:
- Overlay: 8.29
- Ply socks: 6.71
The results suggest that participants perceived a better and more consistent socket fit with the Overlay.
Its pneumatic adjustability may help users respond more precisely when their residual-limb volume changes throughout the day.
3. Cushioning
Participants rated cushioning at:
- Overlay: 8.93
- Ply socks: 6.14
Cushioning showed the largest difference between the two solutions.
Participants consistently perceived the Overlay as providing more cushioning during movement, which may contribute to improved comfort within the socket.
4. Pain levels
Participants rated pain at:
- Overlay: 2.65
- Ply socks: 4.26
For this category, a lower score represents less pain.
Participants reported lower pain levels while using the Overlay. The study authors noted that this may be related to the combination of improved cushioning and socket fit.
5. Ease of use
Participants rated ease of use at:
- Overlay: 8.74
- Ply socks: 5.78
Participants found the Overlay easier to use than traditional ply socks.
Rather than repeatedly adding, removing, or combining different sock thicknesses, the Overlay allows users to adjust the system by adding or releasing air.
What do these results mean?
Across all five categories, participants reported a more positive experience with the Overlay than with prosthetic ply socks.
The findings suggest that an adjustable pneumatic volume-management solution may offer benefits for transtibial amputees who experience:
- A loose prosthetic socket during the day
- Frequent residual-limb volume changes
- Repeated prosthetic sock adjustments
- Pressure or discomfort inside the socket
- A need for additional cushioning
- Difficulty maintaining a consistent socket fit
However, every residual limb, socket, liner, and suspension system is different. Compatibility and proper fitting should always be reviewed with a prosthetist.
Is the Overlay an alternative to prosthetic socks?
The Overlay may serve as an alternative to, or reduce reliance on, prosthetic ply socks for some users.
It does not mean that every amputee will completely stop using socks. Some users may use the Overlay alone, while others may use it as part of a broader volume-management strategy recommended by their prosthetist.
The main difference is adjustability: ply socks provide fixed increases in thickness, while the Overlay allows users to fine-tune volume using air.
Who may benefit from the Overlay?
The Overlay may be relevant for lower-limb amputees who:
- Experience daily limb-volume fluctuations
- Frequently add or remove prosthetic socks
- Notice their socket becoming loose during activity
- Want greater control over socket fit
- Need more cushioning inside the socket
- Find traditional sock management inconvenient
A prosthetist can assess whether the Overlay is compatible with the user’s socket design, liner, suspension method, and clinical needs.
Frequently asked questions
What is the Overlay by Ethnocare?
The Overlay is an adjustable pneumatic prosthetic volume-management solution. It is worn over the prosthetic liner and allows lower-limb amputees to fine-tune their socket fit by adding or releasing air.
How is the Overlay different from prosthetic socks?
Prosthetic socks provide a fixed amount of additional thickness based on their ply. The Overlay uses an adjustable air system, allowing users to make smaller and more precise fit adjustments.
Can the Overlay improve prosthetic socket comfort?
In this internal case study, participants rated comfort higher with the Overlay than with traditional prosthetic ply socks.
Does the Overlay provide cushioning?
Participants rated the Overlay higher for cushioning than ply socks. The pneumatic structure is designed to add adjustable volume and cushioning within the socket.
Can the Overlay reduce pain?
Participants in the internal study reported lower pain scores with the Overlay. Pain can have many causes, so persistent or new pain should always be evaluated by a qualified prosthetist or healthcare professional.
Is the Overlay available for below-knee amputees?
Yes. The Overlay TT is designed for transtibial, or below-knee, amputees.
How can I get an Overlay?
The first step is to speak with your prosthetist. They can review your prosthetic setup, confirm compatibility, and help determine whether the Overlay is appropriate for you.
If you do not currently have a prosthetist, visit ethnocare.ca or contact clinics@ethnocare.ca for guidance.
The bottom line
This internal comparative case study found that participants rated the Overlay more positively than traditional prosthetic ply socks for comfort, socket fit, cushioning, and ease of use, while also reporting lower pain.
For amputees who experience daily socket-fit changes, the Overlay offers an adjustable approach to prosthetic volume management.
Ask your prosthetist whether the Overlay could work with your current setup.
This article summarizes an internal, self-reported case study. The study was not presented as an independent clinical trial, and individual outcomes may vary.
