For many lower-limb amputees, heat and sweat underneath the prosthetic liner are more than minor inconveniences. Trapped moisture can make the residual limb feel hot and uncomfortable, contribute to skin irritation, create odor, and cause movement between the limb and liner.
The Underlay by Ethnocare is designed to help.
The Underlay is an innovative knitted sleeve worn directly against the residual limb, underneath the prosthetic liner. It helps transport sweat away from the skin, support evaporation, manage odor, and create a drier, cooler environment inside the prosthetic socket.
It is now available for transtibial amputees directly from Ethnocare.
What Is the Underlay?
The Underlay is a moisture-management sleeve created specifically for lower-limb prosthesis users.
It is placed directly on the residual limb before the prosthetic liner is donned. Its engineered knitted structure helps move sweat and humidity away from the skin and toward a breathable mesh section that extends beyond the top of the liner.
This exposed textile remains in contact with the air, creating an area where moisture can evaporate more effectively.
The Underlay is approximately 0.5 mm thick per textile layer and adds minimal bulk inside the socket. It can be integrated into an existing prosthetic setup without modifying the socket or significantly changing the user’s normal donning routine.
Why Does Sweat Accumulate Inside a Prosthetic Liner?
A prosthetic liner and socket create a largely enclosed environment around the residual limb.
Silicone, TPE, and TPU liners limit airflow and keep sweat from evaporating as it would from uncovered skin. During physical activity or warm weather, heat and humidity can therefore build quickly inside the liner.
When sweat cannot evaporate, the skin remains warm and wet. This can contribute to:
- Discomfort and excessive heat
- Softening and irritation of the skin
- Friction and rubbing
- Odor and bacterial growth
- Slippage, rotation, or pistoning inside the liner
- Frequent removal of the prosthesis to dry the limb
The Underlay was designed to manage these conditions while the prosthesis is still being worn.
How Does the Underlay Work?
The Underlay combines an engineered textile structure with two Polygiene technologies.
Moisture-Transporting Knit
The knitted pattern moves moisture away from the residual limb and directs it toward the breathable section extending beyond the liner.
Rather than simply holding sweat next to the skin, the textile creates a pathway through which moisture can travel toward an area exposed to airflow.
Breathable Mesh
The proximal mesh section is positioned above the edge of the liner whenever the prosthetic configuration allows it.
Because this section remains exposed to air, it supports the evaporation of moisture transported through the textile.
Polygiene StayFresh®
StayFresh® is an antimicrobial treatment that inhibits the growth of odor-causing bacteria. It helps the Underlay remain fresher during use and reduces the conditions that contribute to persistent odor inside the prosthetic liner.
Polygiene StayCool®
StayCool® is a moisture-activated polymer technology designed to reduce the temperature of the textile by approximately 2–3°C when activated by sweat.
Together, these components help address sweat, humidity, perceived heat, and odor at the skin–liner interface.
Open and Closed Underlay Versions
The transtibial Underlay is available in open and closed configurations.
Underlay TT Open
The open version leaves the distal portion of the residual limb uncovered. This maintains direct contact between the skin and the liner at the distal end.
To use it correctly, the distal edge of the Underlay should be positioned approximately 10 cm, or four inches, above the end of the residual limb. The liner and prosthesis can then be donned as usual.
As much of the proximal mesh section as possible should extend beyond the top of the liner to promote airflow and evaporation.
Underlay TT Closed
The closed version covers the distal end of the residual limb.
It may be appropriate for users with more bulbous limb shapes or for situations in which the clinician or user prefers complete distal coverage. It provides the same core moisture-management, cooling, and antimicrobial features as the open version.
The appropriate model and positioning depend on the residual-limb shape, liner dimensions, suspension system, and individual prosthetic setup.
Does the Underlay Affect Prosthetic Suspension?
Any textile placed between the residual limb and prosthetic liner must be designed with suspension in mind.
Ethnocare evaluated the Underlay through traction testing using 90 N as the benchmark associated with highly demanding activity.
For the open Underlay, the recommended positioning preserves at least 10 cm of direct contact between the residual limb and liner. Initial testing without the textile showed that 10 cm of direct contact generated 300 N of retention.
Additional testing with the Underlay placed beneath the liner also produced retention above the selected 90 N benchmark when positioned according to the instructions.
Correct sizing, positioning, and liner contact remain important. Users should follow the Instructions for Use and consult their prosthetist when determining the appropriate configuration.
What Did Underlay Users Report?
The Underlay was evaluated with 15 lower-limb prosthesis users during daily wear and activities such as walking, cycling, hockey, treadmill exercise, and wheelchair rugby.
Participants reported:
- 51% lower perceived humidity
- 38% lower perceived heat
- An average comfort score of 8 out of 10
Average perceived humidity decreased from 8.4 to 4.1 on a 10-point scale, while perceived heat decreased from 8.3 to 5.2.
In a controlled evaluation using humidity sensors beneath the prosthetic liner, measured relative humidity was reduced by 17% when the Underlay was used.
Humidity also increased more slowly during both rest and walking, suggesting that moisture management begins before intense physical activity.
Who Can Benefit From the Underlay?
The Underlay may be particularly useful for lower-limb amputees who experience:
- Excessive sweating beneath the liner
- Heat buildup inside the prosthetic socket
- Residual-limb humidity or odor
- Moisture-related skin discomfort
- Slippage caused by sweat
- Frequent mid-day removal of the prosthesis for drying
- Increased sweating during sports or exercise
It may also offer additional support for active prosthesis users, people with hyperhidrosis, new amputees adjusting to prosthetic wear, and users whose skin is particularly sensitive to prolonged moisture.
The Underlay should not be worn over an open wound or injury. Users experiencing pain, swelling, altered sensation, or an abnormal skin reaction should discontinue use and consult a qualified healthcare professional.
Compatible Prosthetic Systems
The Underlay is designed for use beneath common prosthetic liner materials, including:
- Silicone liners
- TPE liners
- TPU liners
- Seal-in liners
- Vacuum-compatible liners
Depending on the selected Underlay model and prosthetic configuration, it can be incorporated into systems using:
- Pin-lock suspension
- Lanyard suspension
- Suspension sleeves
- Seal-in systems
- Passive vacuum
- Active vacuum
No socket modification is required.
How Do You Use the Underlay?
The basic donning process is simple:
- Slide the Underlay over the residual limb.
- Position it according to the instructions for the open or closed model.
- Ensure the recommended amount of direct skin-to-liner contact is maintained.
- Don the prosthetic liner and socket normally.
- Keep as much of the breathable proximal section exposed beyond the liner as the setup permits.
After use, remove the socket and liner normally, then slide off the Underlay.
Wash it after each use in water below 40°C with a mild, pH-balanced detergent free from bleach, fragrance, and dye. Allow it to air dry completely before wearing it again.
A New Approach to Prosthetic Sweat Management
Traditional approaches to prosthetic sweating often require users to respond after the liner has already become hot and wet. They may have to remove the prosthesis, dry the limb, change a sock, or interrupt an activity.
The Underlay takes a different approach.
It works continuously beneath the prosthetic liner, helping transport moisture away from the skin while the prosthesis is being worn. Its low-profile design integrates into the existing setup without requiring socket modification.
For lower-limb amputees, that can mean fewer interruptions and a drier, cooler, fresher experience throughout the day.
The Underlay Is Now Available
The Underlay TT is now available directly from Ethnocare.
Explore the available sizes and open or closed configurations, consult the sizing guide, and discover a new approach to managing sweat, heat, moisture, and odor beneath the prosthetic liner.
Visit Ethnocare’s website today to find your size and get your Underlay.
Frequently Asked Questions
What is the Underlay by Ethnocare?
The Underlay is a thin textile sleeve worn on the residual limb beneath a prosthetic liner. It is designed to help lower-limb amputees manage sweat, heat, humidity, and odor.
Does the Underlay require a new socket?
No. The Underlay is designed to be worn inside an existing prosthetic setup without socket modification.
Can athletes use the Underlay?
The Underlay was tested during activities including walking, cycling, hockey, treadmill exercise, and wheelchair rugby. It is intended for both everyday and active use.
Can the Underlay be used with a pin-lock liner?
Yes. The Underlay can be compatible with pin-lock suspension when the correct model, size, and positioning are used.
Can it be used with vacuum suspension?
The closed Underlay can be used with active or passive vacuum systems. Compatibility and positioning should be confirmed based on the individual prosthetic setup.
Is the Underlay machine washable?
Yes. It should be washed after each use below 40°C with a mild, pH-balanced detergent and allowed to air dry completely.
Where can I purchase the Underlay?
The Underlay can be purchased from Ethnocare’s website, right here!
