Elastomer-Biased Artificial Knee Joint for Low-Cost Normative Gait
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Solution Overview
Problem
There is a need for a low-cost, highly functional artificial knee prosthesis suitable for amputees in developing countries, particularly those with above-knee amputations, that addresses the limitations of existing single-axis joints with frequent mechanical failures and high costs, while facilitating normative gait and ease of installation.
Innovation Solution
An artificial knee design comprising first and second knee components connected by a fastener and a flexible elastomeric biasing member, allowing rotation between upright and rotated positions, with a slot and extension member configuration to facilitate movement and a biasing member to return to the upright position, along with a prosthetic leg kit including pylons, connectors, and fasteners for easy assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-axis joints with manual locks are used in above-knee prostheses, then the device complexity is reduced and cost is lowered, but the reliability deteriorates due to frequent mechanical failures and the ease of operation worsens as normative gait is inhibited
Solution Approach 1:
The knee joint is divided into two separate components: a first knee component with a vertical rotation axis and a second knee component with a horizontal rotation axis. This segmentation allows each component to specialize in one rotational movement, improving reliability by reducing mechanical complexity in each individual component while maintaining the overall functionality of multi-axis movement.
Solution Approach 2:
The prosthetic knee joint transitions from a static single-axis design to a dynamic two-axis system that automatically adapts its movement characteristics. The first knee component provides vertical rotation during stance phase, while the second knee component enables horizontal rotation during swing phase, creating a dynamic system that responds to different gait phases without requiring manual intervention or complex control mechanisms.
2Ease of operation
If advanced prosthetic limbs with automatic release and multi-axis movement are designed, then the ease of operation improves and normative gait is facilitated, but the device complexity increases and cost rises making them unaffordable for developing countries
Solution Approach 1:
The complex multi-axis knee joint is segmented into two simpler independent components, each handling a specific rotational axis. This segmentation reduces the complexity of individual components while collectively achieving the functionality of a multi-axis joint, making the overall system more affordable and suitable for developing countries.
Solution Approach 2:
The prosthetic knee joint operates autonomously without requiring manual locks or complex control systems. The automatic release mechanism and multi-axis movement are achieved through the inherent mechanical design of the two-component system, which self-regulates its movement based on the gait phase, eliminating the need for user intervention or complex electronic controls.
3Reliability
If elastomeric members with apertures and bolt-nut arrangements are used to secure knee components, then the reliability improves, but the ease of manufacture decreases and cost increases
Solution Approach 1:
The complex bolt-nut fastening system is extracted and replaced with a simpler integrated connection mechanism. The elastomeric member design is simplified by removing the need for separate apertures and fasteners, instead using a more straightforward attachment method that maintains connection stability while significantly reducing manufacturing complexity and cost.
Solution Approach 2:
The connection between knee components is achieved by merging the fastening function directly into the elastomeric member structure itself, eliminating the need for separate fasteners like bolts and nuts. This integration simplifies the manufacturing process while maintaining the reliability of the connection through the inherent properties of the elastomeric material.
4Ease of operation
If metal spring biasing members are exposed for operation, then the ease of operation improves, but the reliability deteriorates due to potential damage and safety concerns
Solution Approach 1:
The metal spring biasing member is nested within the protective housing of the knee joint, allowing it to perform its function internally while being shielded from external damage. This nesting arrangement maintains user access to the operational functions it controls while protecting the vulnerable spring mechanism from environmental factors and accidental damage that would compromise reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides a lightweight, durable, and affordable prosthetic leg solution that enhances user satisfaction by improving gait and reducing mechanical failures, making it suitable for large-scale use in developing countries.
Implementation Method 1
a biasing member comprising a flexible rod or tube of an elastomeric material operatively associated with the first and second knee components for urging those components towards the upright position. Therefore, rotation of the second knee component toward a rotated position stretches or elongates the biasing member to provide a force that urges the knee components towards the upright position
Data Source
AI summary
An artificial knee that includes a first knee component having an extension member, a second knee component having a slot configured and dimensioned to allow the extension member to move therein. A fastener connects the knee components to facilitate rotation of the knee components between an upright and rotated positions. The knee components also include a terminal end that includes a central opening and transverse apertures to receive pylons therein. A biasing member of a flexible rod or tube of an elastomeric material urges the knee components towards the upright position when the knee components are rotated. The biasing member passes through the apertures of the terminal ends of the knee components, as well as through the extension member and the slot. Also, a prosthetic leg along with a kit and method for assembling the prosthetic leg.