A New Force Myography-Based Approach for Continuous Estimation of Knee Joint Angle in Lower Limb Amputees and Able-Bodied Subjects

In this paper, we present a new method for estimating knee joint angle using force myography. The technique utilized force myogram signals from thigh muscles while subjects walked on a treadmill at different speeds, i.e., slow, medium, fast, and run. An eight-channel in-house force myography (FMG) data acquisition system was developed to collect the data wirelessly from seven healthy subjects and a transfemoral amputee. An artificial neural network was employed to estimate the knee joint angle from force myogram signals. The root-mean-square error across the healthy subjects was 6.9 +/- 1.5 degrees at slow (1.5 km/hr), 6.5 +/- 1.3 degrees at medium (4 km/hr), 7.4 +/- 2.2 degrees at fast (6 km/hr) speeds, and 8.1 +/- 2.2 degrees while running (8 km/hr). The root-mean-square error, across the trials, for the transfemoral amputee was 4.0 +/- 1.2 degrees at slow (1 km/hr), 3.2 +/- 0.6 degrees at medium (2 km/hr) and 3.8 +/- 0.9 degrees at fast (3 km/hr) speeds. The proposed approach is useful in real-time gait analysis. The system is easily wearable, convenient in out-door use, portable, and commercially viable.