Exploratory study of a non-invasive method based on acoustic emission for assessing the dynamic integrity of knee joints

The paper presents the development of a new measurement system based on acoustic emission (AE) for assessing the dynamic integrity of knee joints, and the evaluation of its efficacy, through an exploratory study using healthy and osteoarthritic knees. For the former, the paper describes the system implemented to acquire joint angle-based AE and the protocol developed to obtain repeatable results. For the latter, the paper reports significant differences between healthy and osteoarthritic knees using statistical analysis of AE occurrence and distribution of AE features in different movement phases. Osteoarthritic knees are found to produce 6–10 times more acoustic emissions than healthy knees, with amplitudes which can be 20 dB higher, and durations which can be 10 times longer. These findings lead to a visual representation method of AE feature profiles based on multidimensional density of AE hits per repeated movement and the use of principal component analysis for objective assessment of the clinical status of knee joints.