An Attachable Clothing Sensor System for Measuring Knee Joint Angles

Flexible sensors that can be integrated into clothing to measure everyday functional performance is an emerging concept. It aims to improve the patient´s quality of life by obtaining rich, real-life data sets. One clinical area of interest is the use of these sensors to accurately measure knee motion in, e.g., osteoarthritic patients. Currently, various methods are used to formally calculate joint motion outside of the laboratory and they include electrogoniometers and inertial measurement units. The use of these technologies, however, tends to be restricted, since they are often bulky and obtrusive. This directly influences their clinical utility, as patients and clinicians can be reluctant to adopt them. The goal of this paper is to present the development process of a patient centered, clinically driven design for an attachable clothing sensor (ACS) system that can be used to assess knee motion. A pilot study using 10 volunteers was conducted to determine the relationship between the ACS system and a gold standard apparatus. The comparison yielded an average root mean square error of ~ 1°, a mean absolute error of ~ 3°, and coefficient of determination above (R²) 0.99 between the two systems. These initial results show potential of the ACS in terms of unobtrusive long-term monitoring.