  This paper presents a novel autonomous quality metric to quantify the
rehabilitations progress of subjects with knee/hip operations. The presented
method supports digital analysis of human gait patterns using smartphones. The
algorithm related to the autonomous metric utilizes calibrated acceleration,
gyroscope and magnetometer signals from seven Inertial Measurement Unit
attached on the lower body in order to classify and generate the grading system
values. The developed Android application connects the seven Inertial
Measurement Units via Bluetooth and performs the data acquisition and
processing in real-time. In total nine features per acceleration direction and
lower body joint angle are calculated and extracted in real-time to achieve a
fast feedback to the user. We compare the classification accuracy and
quantification capabilities of Linear Discriminant Analysis, Principal
Component Analysis and Naive Bayes algorithms. The presented system is able to
classify patients and control subjects with an accuracy of up to 100\%. The
outcomes can be saved on the device or transmitted to treating physicians for
later control of the subject's improvements and the efficiency of physiotherapy
treatments in motor rehabilitation. The proposed autonomous quality metric
solution bears great potential to be used and deployed to support digital
healthcare and therapy.
