Goniometric and 3D Motion Analysis in Shoulder ROM Assessment: A Reliability and Agreement Study Comparing Patients With Restricted Shoulder Range of Motion to Healthy Subjects.

Objective: This study aimed to examine the reliability and agreement of goniometric measurements in assessing the range of motion (ROM) within the shoulder joint utilizing a 3D marker-based motion analysis system. Methods: The study comprised 30 healthy volunteers and 35 patients diagnosed with unilateral restricted shoulder range of motion (ROM). Agreement analysis was conducted using Bland-Altman methods, while intra- and interobserver reliability for flexion, abduction, internal rotation, and external rotation measurements was assessed using the Intraclass Correlation Coefficient (ICC). Results: When goniometric measurements were compared with the 3D method, ICC values in the patient group were found to be 0.85 for flexion, 0.81 for abduction, 0.80 for external rotation, and 0.74 for internal rotation. In healthy individuals, the values were found to be 0.80, 0.90, 0.56, and 0.69. Additionally, all measurements fell within acceptable limits of agreement, with no significant differences in measurement biases, except for internal rotation. Conclusion: This study highlights that the goniometer exhibited higher reliability when assessing movements with larger ROM, particularly within heterogeneous groups like those with injured shoulders. However, its reliability decreased when used in homogeneous groups, such as healthy individuals, especially when evaluating movements with narrower ROM, such as rotations. These findings emphasize the need for a nuanced interpretation of results in clinical and research settings when assessing shoulder joint mobility.