Reliability and validity of an iPhone inclinometer as compared to a universal goniometer as a tool for measuring joint motion of the shoulder in apparently healthy subjects

Daniel S. Anderson, Mount St. Mary's College
Eli A. English, Mount St. Mary's College
Kevin B. Varee, Mount St. Mary's College
Deborah Lowe, Mount St. Mary's College
Deborah S. Diaz, University of Texas at El Paso


Background and Purpose: The objective of this study was to evaluate the interrater and intrarater reliability of the iPhone's TiltMeter application and the concurrent validity between the iPhone incinometer and a universal goniometer in measuring shoulder joint motion. No study is currently published examining the reliability and validity of the iPhone inclinometer for use in physical therapy practice. Methods: Participants were positioned supine in two positions of shoulder flexion, 0-90 and 91-180. Each position was measured twice by two examiners with the inclinometer and goniometer. Findings: Intrarater reliability ICCs for the iPhone ranged from 0.92 to .099 and for the goiniometer from .086 to .098. The interrater reliability ICCs for the iPhone ranged from 0.84 to 0.91 and for the goniometer from 0.63 to 0.88. Concurrent validity for for the two devices yielded ICC values ranging from 0.67 to 0.94. Clinical Relevance: Both devices are acceptable for clinical use. However, this was only true when the rater and device were the same for all measurements. The devices should not be used interchangeably.