Reliability of hip rotation range of motion in supine and seated positions

Context: Hip rotation range of motion (ROM) is commonly assessed in individuals with lower extremity or spine pathology. It remains unknown which hip rotation ROM testing position is most reliable. Objective: To compare interrater and intrarater reliabilities between hip internal rotation (IR) and external rotation (ER) ROM in supine and seated positions. Study Design: Controlled laboratory study. Setting: University research laboratory. Participants: A total of 19 participants (11 females and 8 males; age = 23.5 [1.2] y; height = 173.2 [8.6] cm; and mass = 69.2 [13.4] kg) without hip, knee, low back, or sacroiliac pain within the preceding 3 months or history of hip or low back surgery were recruited. Interventions: Three testers obtained measures during 2 testing sessions. Passive supine and seated hip IR and ER ROM were performed with the hip and knee flexed to 90°. Main Outcome Measures: The primary outcome measures were hip IR and ER ROM in supine and seated positions (in degrees). Interrater and intrarater reliabilities were calculated using intraclass correlation coefficients (ICCs). Minimal detectable change was calculated. Differences between supine and seated hip IR and ER ROM values were assessed using paired t tests (significance level was .05). Results: Supine hip IR and ER ROM interrater and intrarater reliabilities were excellent (ICC = .75-.91). Seated hip IR ROM interrater and intrarater reliabilities were good (ICC = .64-.71). Seated hip ER ROM interrater reliability was good (ICC = .65), and intrarater reliabilities were good to excellent (ICC = .65-.82). Minimal detectable change values for supine and seated hip IR and ER ROM ranged from 6.1° to 8.6°. There were significant differences between supine and seated positions for hip IR and ER ROM (41.6° vs 44.5° P < .01 and 53.0° vs 44.2° P < .01, respectively). Conclusion: Supine hip rotation had higher interrater and intrarater reliabilities. Hip IR and ER ROM values differed significantly between supine and seated positions and should not be used interchangeably.