Development and measurement of elbow and knee joints using an electro-goniometer in healthy subjects: A preliminary study

INTRODUCTION: Range of Motion (ROM) assessment is a critical baseline metric for diagnosis, treatment monitoring, and rehabilitation goal setting. It significantly impacts patient well-being, aligning with Sustainable Development Goal 3 (SDG 3). However, the universal goniometer (UG), presents limitations regarding accuracy and practical efficiency in clinical settings. Therefore, this study aimed to determine the concurrent validity of an electronic goniometer named Goniwear compared to the UG for measuring elbow and knee angles. METHODS: The validity of Goniwear involved 40 healthy volunteers stratified by age (20-39 and 40-59 years) and sex. Simultaneous active and passive ROM measurements were conducted three times using both UG and on flexion and extension of the elbow and knee joints. Data were analyzed using the intraclass correlation coefficients (ICC), which were calculated using a two-way random-effects model, and the Bland-Altman method was used to determine the limits of agreement (LoA) between the UG and Goniwear. RESULTS: Reliability between the two instruments ranged from poor to excellent, depending on the joint and movement type. Elbow flexion and extension demonstrated consistently good to excellent reliability in both active and passive conditions (ICC = 0.84-0.91), with minimal bias and relatively narrow LoA. Knee flexion and extension showed poor to moderate reliability (ICC = 0.44-0.55), particularly for extension, accompanied by a wide LoA. CONCLUSION: Agreement between the UG and Goniwear varies across joints and movement conditions. While the instruments appear interchangeable for elbow movements, caution is warranted when interpreting knee ROM due to greater measurement variability. DISCUSSION: The Goniwear demonstrates high validity for single-axis joints with fixed pivot points, suggesting strong potential for clinical application in specific contexts. TRIAL REGISTRATION: The Thai Clinical Trials Registry is TCTR20251120001.