Hip Muscle Strength Is Associated With Symptom Severity in People With Femoroacetabular Impingement Syndrome, but Only in Those With Preexisting Hip Muscle Weakness: A Secondary Analysis of Baseline Data From a Randomized Controlled Trial.

Abstract

<b>OBJECTIVE:</b> To explore associations between hip muscle strength and symptom severity in individuals with femoroacetabular impingement (FAI) syndrome. <b>DESIGN:</b> Cross-sectional study. <b>METHODS:</b> Baseline data from 150 participants with FAI syndrome who participated in a clinical trial were analyzed. Hip abduction, adduction, flexion, extension, internal rotation, and external rotation muscle strength assessments were performed using a handheld dynamometer. Symptom severity was assessed using the International Hip Outcome Tool-33 Symptoms subscale (iHOT-Symptoms). Linear and nonlinear associations were explored using generalized linear models. <b>RESULTS:</b> Nonlinear associations (spline) between hip muscle strength values and iHOT-Symptoms scores were observed. Lower hip flexion (average marginal effect [AME] = 0.25, 95% confidence interval [CI] [0.12, 0.39]), abduction (AME = 0.25, 95% CI [0.11, 0.40]), and adduction (AME = 0.29, 95% CI [0.11, 0.47]) muscle strength values were associated with worse iHOT-Symptoms scores. Greater hip muscle strength was not associated with better iHOT-Symptoms scores. Hip external rotation (AME = 0.10, 95% CI [-0.01, 0.20]), internal rotation (AME = 0.10, 95% CI [0.01, 0.19]), and extension (AME = 0.02, 95% CI [-0.02, 0.07]) muscle strength values were not meaningfully associated with iHOT-Symptoms scores. <b>CONCLUSION:</b> Reduced hip flexion, abduction, and adduction muscle strength were associated with worse symptoms in patients with FAI syndrome, but only in individuals with hip muscle weakness. Hip external rotation, internal rotation, and extension muscle strength were not associated with symptom severity. <i>J Orthop Sports Phys Ther 2026;56(7):465-471. Epub 2 March 2026. doi:10.2519/jospt.2026.13674</i>.