# Acoustic Emission Biomarkers for the Detection and Monitoring of Early Knee Osteoarthritis: Protocol for a Prospective, Single-Center, Exploratory Study

## TL;DR

This study explores using knee sounds to detect early osteoarthritis, aiming to identify acoustic biomarkers for early diagnosis and monitoring.

## Contribution

The study introduces a novel approach using acoustic emissions as potential biomarkers for early osteoarthritis detection.

## Key findings

- Acoustic emissions from knee movements will be analyzed alongside MRI and KL scores to identify correlations.
- Thermal imaging will be used to assess inflammation alongside acoustic data.
- Health-related questionnaires will provide subjective data to correlate with objective acoustic and imaging findings.

## Abstract

Osteoarthritis is a highly prevalent and disabling condition. In early stages, patients are asymptomatic or only experience activity-related pain. When pain intensifies, the disease has often progressed, with few treatment options besides knee arthroplasty. Recently, there has been a growing interest in acoustic emissions generated by poorly lubricated and/or damaged moving joint surfaces, as seen in osteoarthritis. Noninvasive analysis of knee sound could help identify patients with early-stage osteoarthritis at a low cost, without radiation exposure. Thus, preventive measures could be implemented earlier and delay the progression of osteoarthritis.

This study aims to identify acoustic biomarkers with prognostic value for the early detection of osteoarthritis. To achieve this, a preliminary reference database will be developed using a subpopulation at risk of developing osteoarthritis, incorporating acoustic signals and gold-standard clinical measures for validation.

A total of 100 patients with previous reconstructive knee surgery and 20 healthy controls will be examined twice at a 9-month interval for both knees. Acoustic emissions (AE) will be recorded with the Inmodi knee brace (École Polytechnique Fédérale de Lausanne; EPFL) during 4 functional tests (unloaded flexion-extension, sit-to-stand test, one-step test, and walk test). Gold-standard osteoarthritis diagnostics will be assessed and evaluated by an experienced radiologist for (1) the magnetic resonance imaging (MRI) Osteoarthritis Knee Score (MOAKS) and (2) the Kellgren-Lawrence (KL) grading scores. Feature analysis and multivariate modeling will be used to study the association between the extracted sound parameters and osteoarthritis (MOAKS and KL). In addition, thermal images will be taken to investigate the state of inflammation. Participants will fill out 5 health-related questionnaires (Oxford Knee Score [OKS], Core Outcome Measures Index [COMI], University of California at Los Angeles [UCLA ]activity scale, Knee Injury and Osteoarthritis Outcome Score [KOOS], and Forgotten Joint Knee Score-12 [FJS-12]) at both time points.

Recruitment and data collection started in December 2022. In November 2023, data collection of all 120 participants (female: n=49, 41%) was completed for the first visit. The data collection for the second visit will end in 2024. Preliminary data processing and analysis are ongoing at the time of this writing.

This exploratory study will contribute to a better understanding of the disease progression of osteoarthritis and the use of acoustic biomarkers for predicting osteoarthritis.