KneeMS to Monitor Knee Acoustic Emissions for Juvenile Idiopathic Arthritis

Objective: Wearable sensing for capturing knee acoustic emissions (KAEs) can enable earlier detection and better management of juvenile idiopathic arthritis (JIA). In this paper, we expand on our previous work by validating the KneeMS wearable for individuals with JIA in a clinical setting against a benchtop system (Dytran).Methods and procedures: Acoustic features were recorded from the medial and lateral sides of the patellar tendon using both Dytran and KneeMS in 36 participants with JIA during flexion/extension (FE). We calculated the Spearman correlation coefficient ( ρ ) between the acoustic features of both devices Acoustic features were recorded from the medial and lateral sides of the patellar tendon using both Dytran and KneeMS in 36 participants with JIA during flexion/extension (FE). We calculated the Spearman correlation coefficient between the acoustic features of both devices and assessed severity trends and longitudinal tracking of JIA knees from a machine learning (ML) pipeline differentiating active from inactive JIA knees.Results: Of 36 extracted features, six had the highest ρ (medial/lateral): RMS (0.79/0.70), MFCC1 (0.79/0.72), spectral slope (0.78/0.68), energy (0.78/0.67), Hjorth activity (0.75/0.71), and spectral flux (0.74/0.69). Our ML pipeline demonstrated an area under the receiver operating characteristic curve (AUC-ROC) mean of 0.77 ( p< 0.05 ) and showed a significant ( p< 0.05 ) upward trend in active knee prediction probabilities $P(A)$ with clinical severity using KneeMS. For follow-ups, KneeMS $P(A)$ moved in the clinically expected direction for 4 of 5 status-changing knees (versus 1 of 5 for Dytran); the clinical JADAS (cJADAS) score, available for most knees, was consistent with this finding.Conclusion: The high correlation between the acoustic features of Dytran and KneeMS, a significant AUC-ROC, significant JIA severity trend, and prospective longitudinal tracking make KneeMS a viable alternative to Dytran.Clinical impact: This validation establishes the foundation of home-based longitudinal joint assessment for JIA.Clinical and Translational Impact Statement: Wearable acoustic monitoring could enable at-home tracking of JIA disease activity, supporting timely treatment.