Objective measuring knee joint laxity in knee osteoarthritis using wearable sensors: a pilot study

Abstract

Purpose: Knee Osteoarthritis (OA) is a degenerative joint disease, specifically degeneration of the cartilage leading to pain, stiffness, swelling, and tenderness. It is clinically understood that knee joint instability correlates to the onset of OA. The majority of current research on knee laxity is limited to subjective, self-reported questionnaires based on perceived instability or physician reported laxity based on manual manipulation of the knee. Research findings on objective measurements of knee laxity are limited therefore the purpose of our pilot work is to develop wearable sensors based system to quantify knee laxity in OA objectively, which is critical to understand the function of Knee OA. Methods: We used wearable sensors of measuring kinematics (the anterior-posterior placement of the tibia relative to the patella) and kinetics (the load applied to the tibia) to build measuring mechanism that the system is strapped to the anterior portion of the lower leg with one pad in contact with the patella and the other in contact with the tibia. Also a load handle is attached to the system. The displacement and load signals mentioned above are fed into a single board computer (SBC) utilizing microprocessor. This allows us to quantify the displacement of the tibia relative to the patella under various load conditions (-15, 15, 20, and 30 pounds). We obtained measurements of knee laxity in 5 knee OA patients (Age: 46-75; Gender: 4 Females, 1 Male; Body Weight: 57.2Kg-109.3Kg; Body Height: 1.46-1.78M). The knee laxity were compared between OA side and non-OA side using paired t-test at α=0.05. Results: We found that the laxity of OA side is significantly higher (4.902 +/- 2.734 mm) than non-OA side (3.530 +/- 2.170 mm) at the 30lbs load condition (P<0.05). Conclusions: This pilot study is designed to use wearable sensors to measure knee laxity objectively in knee OA. Our results are consistent with previous studies in a similar range. We believe our pilot study results suggest that the wearable system can be a portable solution to monitor knee joint function of knee OA patients in various clinical settings and their responses to different types of clinical treatments.