Concurrent validity and reliability of the Simple Goniometer iPhone app compared with the Universal Goniometer

Area of Science:

• Biomechanics
• Digital Health Technology
• Musculoskeletal Assessment

Background:

• Accurate joint angle measurement is crucial for diagnosing and managing musculoskeletal conditions.
• Traditional goniometers require manual operation and can be subject to user variability.
• Mobile health applications offer potential for accessible and objective clinical assessments.

Purpose of the Study:

• To evaluate the concurrent validity and reliability of the Simple Goniometer (SG) iPhone app.
• To compare the SG app's knee joint angle measurements against the established Universal Goniometer (UG).

Main Methods:

• A within-subject comparison design was employed.
• Thirty-six participants had their knee joint angles measured during standing lunges using both the SG app and the UG.
• Statistical analyses included Pearson correlations and intraclass correlation coefficients, supplemented by the Bland-Altman method.

Main Results:

• No significant differences were found between the SG app and UG measurements for knee joint angles.
• High Pearson correlations (0.96-0.98) and intraclass correlation coefficients (0.97-0.99) indicated strong agreement.
• The Bland-Altman analysis revealed low standard errors and standard deviations of differences, supporting measurement consistency.

Conclusions:

• The Simple Goniometer iPhone app demonstrates reliable performance and concurrent validity when compared to the Universal Goniometer.
• The findings support the use of the SG app as a valid tool for measuring knee joint angles in similar populations and protocols.
• Mobile goniometry presents a viable alternative for objective musculoskeletal assessments.