Clinical and Instrumented Measurements of Hip Laxity and Their Associations With Knee Laxity and General Joint Laxity

Abstract

Context: Hip-joint laxity may be a relevant anterior cruciate ligament injury risk factor. With no devices currently available to measure hip laxity, it is important to determine if clinical measurements sufficiently capture passive displacement of the hip. Objective: To examine agreement between hip internal-external–rotation range of motion measured clinically (HIERROM) versus internal-external–rotation laxity measured at a fixed load (HIERLAX) and to determine their relationships with knee laxity (anterior-posterior [KAPLAX], varus-valgus [KVVLAX], and internal-external rotation [KIERLAX]) and general joint laxity (GJL). Design Cross-sectional study. Setting: Controlled research laboratory. Patients or Other Participants: Thirty-two healthy adults (16 women, 16 men; age = 25.56 ± 4.08 years, height = 170.94 ± 10.62 cm, weight = 68.86 ± 14.89 kg). Main Outcome Measure(s): Participants were measured for HIERROM, HIERLAX at 0° and 30° hip flexion (−10 Nm, 7 Nm), KAPLAX (−90 N to 133 N), KVVLAX (±10 Nm), KIERLAX (±5 Nm), and GJL. We calculated Pearson correlations and 95% limits of agreement between HIERROM and HIERLAX_0° and HIERLAX_30°. Correlation analyses examined the strength of associations between hip laxity, knee laxity, and GJL. Results: The HIERROM and HIERLAX had similar measurement precision and were strongly correlated (r > 0.78). However, HIERROM was systematically smaller in magnitude than HIERLAX at 0° (95% limits of agreement = 29.0° ± 22.3°) and 30° (21.4° ± 19.3°). The HIERROM (r = 0.51–0.66), HIERLAX_0° (r = 0.52–0.69) and HIERLAX_30° (r = 0.53–0.76) were similarly correlated with knee laxity measures and GJL. The combinations of KVVLAX and either HIERROM, HIERLAX_0°, or HIERLAX_30° (R2 range, 0.42–0.44) were the strongest predictors of GJL. Conclusions: Although HIERROM and HIERLAX differed in magnitude, they were measured with similar consistency and precision and were similarly correlated with knee laxity and GJL measures. Individuals with greater GJL also had greater hip laxity. These findings are relevant to clinicians and investigators conducting prospective risk factor studies, given the need for accessible, efficient, and low-cost alternatives for characterizing an individual's laxity profile.