Acoustic emission biomarkers for the detection and monitoring of early knee osteoarthritis. Protocol for a prospective, single-center, exploratory study. (Preprint)

BACKGROUND Osteoarthritis (OA) 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 OA. Non-invasive analysis of knee sound could help identify patients with early-stage OA at a low cost, without radiation exposure. Thus, preventive measures could be implemented earlier and delay the progression of osteoarthritis. OBJECTIVE This project aims to identify acoustic biomarkers with prognostic value for the early detection of OA. To achieve this, a preliminary reference database will be developed using a subpopulation at risk of developing OA, incorporating acoustic signals and gold-standard clinical measures for validation. METHODS 100 patients with previous reconstructive knee surgery and 20 healthy controls will be examined twice at a nine-month interval for both knees. Acoustic emissions (AE) will be recorded with the inmodi knee brace during four functional tests (unloaded flexion-extension, sit-to-stand test, one-step test, and walk test). Gold-standard OA diagnostics will be assessed and evaluated by an experienced radiologist for (1) the 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 OA (MOAKS and KL). In addition, thermal images will be taken to investigate the state of inflammation. Participants will fill out five health-related questionnaires (Oxford Knee Score, Core Outcome Measures Index, University of California at Los Angeles activity scale, Knee Injury and Osteoarthritis Outcome Score, Forgotten Joint Knee Score-12) at both time points. RESULTS 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 currently ongoing. CONCLUSIONS This exploratory study will contribute to a better understanding of the disease progression of OA and the use of acoustic biomarkers for predicting OA. CLINICALTRIAL ClinicalTrials.gov ID: NCT06351059