Decreased range of motion is associated with structural hip deformity in asymptomatic adolescent athletes

Background: Decreased hip range of motion (ROM) is a common finding in patients with femoroacetabular impingement (FAI). Purpose: To report the prevalence of decreased hip ROM in asymptomatic adolescent athletes and to correlate examination findings to signs of FAI on radiographs and magnetic resonance imaging (MRI). Study Design: Cross-sectional study (prevalence); Level of evidence, 3. Methods: A total of 226 adolescent athletes presenting for state-mandated preparticipation physical examinations were assessed. Hip internal rotation was measured with the participant supine and the hip flexed to 90°. All participants with <10° of internal rotation were invited to return for standard radiographs and MRI of both hips. An age-matched control group, with >10 of internal rotation, underwent MRI examination only. Twenty-six athletes (13 study and 13 control) returned for clinical and radiographic examinations. Results: Nineteen athletes (34 hips, 8%) were found to have <10° of internal rotation. Eight athletes (13 hips, 3%) also had a positive anterior impingement sign. Thirteen of 19 athletes participated in the radiographic portion of the study. Of these 13 participants, 4 had limited internal rotation unilaterally, leaving 22 hips in the study group. Eight of 13 participants (15 hips, 68%) had a cam-type deformity evident on plain radiographs, and 4 participants (7 hips, 32%) had a positive radiographic crossover sign. The average a angle measured from radial MRI sequences was 58.1° in the study group versus 44.3° in the control group (P<.001). Fifteen hips (68%) in the study group had abnormal MRI findings within the acetabular labrum or cartilage compared with 10 of 26 hips (38%) in the control group (odds ratio, 3.4; P = .078). Conclusion: Eight percent of asymptomatic teenagers had limited internal rotation on examination; 68% of these had radiographic findings suggestive of FAI. More than two thirds of these participants had evidence of asymptomatic hip pathological lesions on MRI.