退化性關節炎為目前造成老年人失能的四大慢性疾病之一,世界衛生組織也預估 在2020年全球將有25%人口患有此疾病。此研究藉由探討退化性關節炎的病因, 進而提出一套穿戴式系統iKneePad,利用九軸加速度器去量測大小腿的尤拉角 度,去推算即時膝蓋角度的變化,並利用膝蓋角度在行走時的週期變化,得出行 走步數以及步距的計算。此研究也是第一個提出利用角度變化以及大小腿的長度 在幾何層面去推算步數以及步距。實驗結果顯示步數能達到 100%準確率,在步 距上誤差也小於3%。

Background: Knee angle is a significant factor related to knee function, degeneration, and loading for patients with knee osteoarthritis (OA). However, there is no system that can monitor and record the knee angle outside the laboratory in our daily life.

Research question: To calculate the knee angle, stride counts, and walking distance and provide instant feedback on his own smartphone.

Methods: We propose a system, iKneePad, fusing two 9-axial sensors with Bluetooth equipped on the thigh and shank segments to calculate knee angle. Furthermore, we use the changing rates of hip and knee angles to determine the beginning and the ending of a stride. Last, we use thigh length, shank length, hip angle, and knee angle to calculate the walking distance.

Results: The experimental results show that the accuracy of stride count is 100%, the absolute mean errors of knee angle are 2.99◦ and 1.42◦ for the maximum and minimum flexion angles, respectively. For walking distance, the mean error rates are -2.40% and -2.26% for short (10m) and long (33m) distances, respectively.

Significance: The first system that can calculate knee angle, stride count, and walk- ing distance with acceptable errors and instantly provide feedback to users by showing on an Android smartphone when doing rehabilitation or exercise with iKneePad.

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