Evolutionary Denoising-Based Machine Learning for Detecting Knee Disorders

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Evolutionary Denoising-Based Machine Learning for Detecting Knee Disorders Luca Parisi1,2

· Narrendar RaviChandran2

Accepted: 30 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract Surface electromyography (sEMG) is a non-invasive tool that can aid physiological assessment of knee disorders towards clinical interventions. Machine Learning (ML) is widely used to classify sEMG data to help with early detection of knee disorders; however, the inherent noise and the high non-linearity of sEMG signals make pattern recognition a challenging task. This study aims to partly overcome these challenges with existing ML-based classifiers by denoising sEMG signals further via an innovative two-fold evolutionary approach. A novel Genetic Algorithm-based denoising approach is applied to sEMG data to decrease the search space for pattern-related classification. Thereafter, the proposed denoising technique is coupled with an ML-based classifier to improve the discrimination between physiological and pathophysiological knee functions from sEMG data by optimising its hyperparameters too. Thus, the novel evolutionary approach serves two purposes. Firstly, it further reduces noise in sEMG signals via a new GA-based denoising technique to concurrently maximise mutual information and minimise entropy; secondly, it also enables the optimisation of the classifier’s hyperparameters. The classification performance of the resulting hybrid algorithm was validated using sEMG data on 144 subjects (67 patients with knee disorders, 77 healthy subjects) and was found higher (ACC  99.57%, 95% CI: 99.47–99.66; AUC  1, 95% CI: 0.98–1) than that of similar ML algorithms and published studies. The hybrid algorithm achieved the highest classification performance by leveraging an evolutionary approach for effective denoising and hyperparameter optimisation, whilst retaining the lowest computational cost. Thus, the proposed evolutionary denoising ML-based classifier is deemed an accurate and reliable decision support system to aid the detection of knee disorders. Keywords Diagnosis · Decision support system · Machine learning · Support vector machine · Knee disorder · Genetic algorithm

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Luca Parisi [email protected] Narrendar RaviChandran [email protected]

1

Faculty of Business and Law (Artificial Intelligence Specialism), Coventry University, Coventry, UK

2

University of Auckland Rehabilitative Technologies Association (UARTA), University of Auckland, Auckland, New Zealand

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L. Parisi, N. RaviChandran

1 Introduction Knee-related disorders are mainly caused by abnormal loading on the knee joint [1, 2]. Such abnormalities are exacerbated by the ageing process and co-morbidities, such as obesity and lower limb misalignments. With an alarming incidence of 20–30% in the elderly population [1], knee osteoarthritis is one of the leading causes of disability worldwide. Such knee disorders require prompt surgical intervention, like total knee replacement or hightibial osteotomy, and, additionally, mont