More is not always better-association between hip range of motion and symptom severity in patients with femoroacetabular impingement syndrome: A cross-sectional study

Restricted hip range of motion (ROM) is a common finding in patients with femoroacetabular impingement (FAI) syndrome. However, the association between hip ROM and symptom severity in these individuals is unclear. Explore associations between symptom severity and hip flexion and rotation ROM in patients with FAI syndrome and determine if ROM measures can discriminate those with worse symptoms. Data from 150 participants with FAI syndrome were analysed. A digital inclinometer was used to measure hip flexion, internal rotation, and external rotation ROM. Symptom severity was quantified using the symptoms subscale of the international Hip Outcome Tool questionnaire (iHOT-Symptoms). Multivariable fractional polynomial analyses explored associations between hip ROM measures and symptom severity. Receiver operator characteristic curves explored the ability of ROM measurements to discriminate participants with different symptomatic states. Smaller hip flexion ROM values were associated with worse iHOT-Symptoms scores (p < 0.01; R2=0.242); with the polynomial concave association attenuated at approximately 120° of hip flexion ROM. Hip internal rotation was weakly associated with iHOT-Symptoms score (p = 0.01; R2=0.033). Hip external rotation ROM was not associated with iHOT-Symptoms score (p = 0.06). A hip flexion value of 107° best discriminated mild to moderate and severe symptom states (sensitivity 92%, specificity 52%). Less hip flexion ROM was associated with worse symptoms in patients with FAI syndrome. Patients with hip flexion ROM ≥ 107° had a 15-fold decrease in the likelihood of having severe symptoms. Hip rotation ROM measures do not have a clinically meaningful association with symptom severity.