Reliability of hip internal rotation range of motion measurement using a digital inclinometer

Purpose: Assessment of hip internal rotation (IR) is a critical element in the evaluation of a painful hip, yet there currently exists no consistent method of determining this measurement. The purpose of this study is to report the intra-rater and inter-rater reliability of active and passive hip IR measurement using a digital inclinometer. Methods: Twenty-five subjects (8 men, 17 women) with asymptomatic hip joints, and no known pathology between the ages of 22 and 42 participated. Two examiners measured hip IR for each subject using a digital inclinometer while visually monitoring pelvic motion. Measurements included passive IR, active IR, and active IR while internally rotating both legs simultaneously. Statistical analysis was performed including intra-rater and inter-rater reliability. Results: There was no significant difference in measured IR values. Mean range of motion values for all techniques and both examiners ranged from 30.7° to 32.8°. Intra-rater reliability for examiner 1 ranged from 0.84 to 0.92. Inter-rater reliability ranged from 0.89 to 0.93. Of the methods utilized, active IR of a single leg was the most responsive technique with a minimal detectable change value of 5.4°. Conclusions: Clinical assessment of hip IR range of motion can be performed efficiently and reliably with a digital inclinometer along with visual monitoring of the pelvis for unwanted motion. Findings from this study support unilateral active hip IR in a seated position as a reliable and responsive technique for obtaining hip IR measurements. Level of evidence: III.