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Problem
Problem
Quadricep weakness is a common issue following hip arthroplasty, ACL reconstruction, and osteoarthritis, often resulting in knee buckling during walking. Traditional braces typically lock the knee or restrict motion, which improves stability but limits mobility and prevents patients from maintaining a natural gait.
My objective was to create a device that:
• Prevents knee buckling when most vulnerable (heel strike/stance phase).
• Maintains natural gait without permanently locking the joint.
• Is lightweight and comfortable for daily activities.
Approach
Approach
I worked with my team to design a novel external brace that could proactively stabilise the knee without locking it. Using CAD (Creo), we modeled the brace with lightweight aluminium side rails and polypropylene back plates. To provide dynamic support, I integrated custom torsion springs engaged through a steel ratcheting system (seen to the right).
To control support activation, I programmed a microprocessor (based in C/C++) and utilized IMU sensors to track knee flexion angle and angular acceleration. With additional data analysis, the springs could then engage during the stance phase and disengage during the swing phase. To ensure safety, Finite Element Analysis (FEA) of the ratcheting system was conducted for mechanical safety, while regulatory standards (primarily ISO 22523:2006 & IEC- 60610–1) were followed for electronics and software. We fabricated and assembled the prototype, then ran bench-top gait trials to confirm activation timing and user comfort.
Solution
Solution
The final brace produced a combined torque of 0.3 Nm/° during the stance phase, effectively resisting knee buckling when the joint was most vulnerable. User testing confirmed the spring engagement system activated precisely at heel strike and disengaged during swing, preserving a full range of motion (0°–136°). The prototype weighed only 3.75 lbs and could be donned in under two minutes, making it practical for patient use.
By combining user need assessment, biomechanics analysis, CAD/FEA design, sensor programming, and prototype testing, this device demonstrated a feasible solution for increasing mobility and independence in patients with quadricep weakness without sacrificing natural gait patterns.
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