Accuracy and reliability of remote shoulder motion capturing methods: a systematic review and meta-analysis

Background: The COVID-19 pandemic accelerated the demand for remote assessment tools in rehabilitation, especially the need for accurate and reliable technologies to measure shoulder range of motion (ROM) outside of clinical environments. Emerging tools such as smartphone apps, wearable sensors, and markerless motion capture systems are increasingly being adopted, yet their accuracy and reliability compared to reference standards remains unclear. Objective: To systematically evaluate the accuracy and reliability of existing remote shoulder ROM measurement technologies, quantify measurement bias, and assess their agreement with reference standards. Methods: A systematic review and meta-analysis was conducted on 26 studies evaluating remote ROM measurement tools. Pooled mean bias (in degrees) was calculated as the primary effect size for agreement, with reliability assessed using intraclass correlation coefficients (ICCs). Subgroup analyses were performed by motion type, technology category, population health status, and data acquisition method. Risk of bias was assessed using the QUADAS-2 tool. Results: Remote measurement methods showed a small but consistent overestimation of ROM compared to reference standards (pooled mean bias = 2.63°, 95% CI: 1.52-3.74), particularly in flexion, internal rotation, and external rotation. No significant bias was observed in abduction or extension. Both IMU and non-IMU technologies demonstrated comparable levels of overestimation. Pathologic populations exhibited greater variability (bias = 4.33° vs. 2.37° in healthy subjects). Self-measurements showed lower and non-significant bias compared to assessor-guided methods. Reliability was generally high, especially for test-retest assessments (ICCs > 0.90), though more variable in inter-rater and pathological settings. Conclusion: Remote shoulder ROM measurement technologies tend to slightly overestimate joint angles but remain within clinically acceptable limits. These tools are reliable for tracking ROM trends and suitable for remote monitoring in clinical and research settings. However, increased variability in pathologic populations warrants caution. Broader validation in diverse patient cohorts is needed to strengthen clinical implementation.