Prosthetic Knee Joint Stance Phase Flexion
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Solution Overview
Problem
Prosthetic knee joints with variable-length joints face complexity and the risk of geometric lock during stance phase flexion, which limits their ability to bend effectively.
Innovation Solution
A prosthetic knee joint design featuring a four-member joint system with fixed-length joints and a spring element that counters inflection through a strategically aligned spring force, preventing geometric lock by allowing flexion even during stance phase, with the spring element's line of action increasing the moment against bending as the joint system pivots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If variable-length joint elements are used in the prosthetic knee joint, then flexion during stance phase is enabled, but device complexity increases
Solution Approach 1:
The patent changes the parameter of joint member length from variable to fixed, eliminating the complexity of variable-length mechanisms while maintaining flexion capability through a different mechanism (spring-loaded counterbalance system)
Solution Approach 2:
The patent replaces the variable-length mechanical adjustment system with a spring-based counterbalance mechanism that provides automatic length compensation through elastic deformation, reducing mechanical complexity
2Ease of operation
If variable-length joint elements are used to enable stance phase flexion, then bending is possible, but geometric locking occurs
Solution Approach 1:
The patent introduces a spring element that acts as a counterbalance, providing a counteracting moment to prevent geometric locking during stance phase flexion. The spring force compensates for the gravitational moment, ensuring smooth bending motion without locking
Solution Approach 2:
The spring element is pre-loaded to provide a counterbalancing moment before flexion occurs, preventing the geometric locking condition from developing in the first place by maintaining proper force balance throughout the motion range
3Device complexity
If the joint system is made simpler with fixed-length members, then device complexity is reduced, but the ability to counteract flexion forces is weakened
Solution Approach 1:
The spring element acts as an intermediary component that transmits and amplifies the counterbalancing force. By positioning the spring at a specific lever arm distance from the pivot axis, a relatively small spring force generates a large counterbalancing moment, maintaining force effectiveness while using simple fixed-length members
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
Enables the prosthetic knee joint to flex during stance phase without geometric lock, ensuring stability and simplicity in construction, allowing for effective bending through a hip flexion moment, thus preventing unintended bending and maintaining safety during heel strikes.
Implementation Method 1
the joint system is pivotably mounted on the lower part from an initial position against a spring force during the stance phase flexion
Data Source
Figure 1
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AI summary
The invention relates to a prosthetic knee joint comprising an upper part (10), a lower part (20) which is arranged pivotably to the upper part (10), a fastening device (11) arranged on the upper part (10) for a proximal prosthetic element, a fastening device (21) arranged on the lower part (20) for a distal prosthetic element, a four-limbed joint system (100) with four linkages (30, 40, 50, 60) articulatedly fastened to each other, which are each pivotable to each other around a pivot axis (1, 2, 3, 4), wherein the upper part (10) is arranged on the joint system (100), wherein the joint system (100) is mounted pivotably on the lower part (20) from a starting position counter to a spring force during a stance phase flexion, and the action line (F) of the spring force is aligned such that a moment acting against an inflexion of the joint system (100) is present.