Reliability of range of motion in straight leg raise and hip extension tests among healthy young adults using a smartphone application

Introduction

Measuring range of motion (ROM) is an important skill for clinicians because it can help in the accurate interpretation of a patient's condition. Recently, ROM tests using smartphone applications have been performed in clinical settings, with the tests demonstrating high reliability and validity. This study aimed to identify the usefulness of ROM tests conducted using smartphone applications by examining the reliability of straight leg raise (SLR) and hip extension (HE) tests.

Methods

This cross-sectional observational study included 72 lower limbs of 36 participants (19 men and 17 women; mean age, 21.6 ± 0.8 years). Passive SLR-ROM and HE-ROM were measured in 1° increments using an iPhone goniometer (IG). Intra-rater and inter-rater reliabilities were calculated using intraclass correlation coefficients (ICCs). ROM test systematic error was confirmed using Bland–Altman analysis, and ROM measurement error was calculated.

Results

The ICCs of the IG ROM tests were 0.820 or higher. According to Bland–Altman analyses, SLR-ROM and HE-ROM did not acknowledge fixed and proportional biases. Thus, ROM measurement error was calculated as the minimal detectable change (MDC). The intra-rater and inter-rater MDC 95% confidence interval (MDC₉₅) values of SLR-ROM were 3.3° and 10.2°, respectively. The intra-rater and inter-rater MDC₉₅ values for HE-ROM were 3.9° and 9.6°, respectively.

Conclusion

IG ROM tests were highly reliable, simple, and easy to perform. SLR-ROM and HE-ROM tests conducted using smartphone applications may be useful indices for clinical decision-making.