Progressive Force Strap Assembly for Multi-Angle Knee Unloading

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Solution Overview

Problem

Conventional dynamic force straps in knee braces provide unloading only at low flexion angles, failing to support the knee at greater angles required during activities like walking up stairs, and are inadequate for microfracture surgery indications.

Innovation Solution

A progressive force strap assembly with an elongate inelastic body and elastic body, featuring a tension limiter and dosing device, maintains a consistent force over a range of motion, allowing unloading at various flexion angles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional dynamic force straps are used, then unloading is achieved at low flexion angles, but unloading is not provided at greater flexion angles required during activities like stair ascent

Engineering Contradiction:

Improverange of flexion angles for unloadingVSAvoidconsistency of unloading force

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The strap assembly uses an elastic body that dynamically adjusts its tension based on the degree of knee flexion. The elastic material progressively engages as flexion increases, providing adaptive unloading force that scales with the required support level across different activity intensities and flexion angles

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the physical parameter of strap tension by incorporating an elastic body with specific elasticity characteristics. This allows the tension force to vary continuously with flexion angle, transforming the static tension of conventional straps into a dynamic parameter that adapts to different functional requirements

Inventive Principle:

Principle #35Parameter changes

2Force

If conventional dynamic force straps become taut, then unloading force is applied, but the straps only become taut when the knee is close to full extension

Engineering Contradiction:

Improveunloading forceVSAvoidactivation range during gait cycle

Core Design Contradiction:

ForceVSEase of operation

Solution Approach 1:

The elastic body is pre-configured with a specific unstretched length and elasticity to begin engaging earlier in the flexion range. This preliminary action ensures that the unloading force activates progressively as flexion increases, rather than waiting until full extension is approached

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The strap transitions from a static, all-or-nothing tension system to a dynamic system where the elastic body progressively engages based on flexion angle, making the unloading force available throughout the functional gait cycle including stair ascent activities

Inventive Principle:

Principle #15Dynamics

3Reliability

If an elastic body is used to provide progressive force, then consistent unloading is achieved throughout gait cycle, but the strap assembly becomes more complex

Engineering Contradiction:

Improveconsistency of unloading forceVSAvoidstrap assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of adding complex mechanical control systems, the invention achieves progressive force delivery by changing the fundamental parameter of the strap material itself - using an elastic body with specific elasticity characteristics. This material-based solution is simpler than mechanical control systems while providing reliable, consistent unloading throughout the gait cycle

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The elastic body automatically regulates the unloading force based on the knee flexion angle without requiring external control mechanisms. The material's inherent elasticity properties enable it to self-adjust the tension force, eliminating the need for complex control systems while maintaining consistent and reliable unloading

Inventive Principle:

Principle #25Self-service

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 progressive force strap assembly provides consistent unloading throughout the gait cycle, improving pain relief and supporting microfracture surgery rehabilitation by maintaining a minimum force on the joint, enhancing comfort and compliance.

Implementation Method 1

an elastic body having first and second ends. The first end of the elastic body is secured to the second end of the inelastic body, is arranged to stretch a plurality of lengths, and has a maximum stretchable length

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS12427048B2Progressive force strap assembly for use with an orthopedic device

Publication Date: 2025.09.30 OSSUR HF

AI summary

A progressive strap assembly includes an elongate, inelastic body having first and second ends, and an elastic body having first and second ends, the first end of the elastic body anchored to the second end of the inelastic body. The elastic body is arranged to stretch a plurality of lengths and has a maximum stretchable length. A tension limiter is connected to the first and second ends of the elastic body and is arranged to inhibit a predetermined stretchable length of the elastic body short of the maximum stretchable length.