Assessment of the alpha angle and mobility of the hip in patients with noncontact anterior cruciate ligament injury.

Purpose: To evaluate the alpha angle of the hip in patients with noncontact anterior cruciate ligament (ACL) injury and compare it with patients without injury. In addition, external and internal rotation of the hip was assessed and correlated with the alpha angle.

Methods: The alpha angle of the ipsilateral hip was assessed in 41 subjects with non-contact ACL tear and compared with 39 subjects with no tear. The external and internal rotation of the ipsilateral hip was also evaluated.

Results: The alpha angle was larger in subjects with noncontact ACL injury. The mean was 70.31° (±13.92°) compared with 58.55° (±13.95°) in the control group (p < 0.001). The groups were similar when considering the external, internal, and sum of rotation of the ipsilateral hip. There was no correlation between the alpha angle and decreased rotational range of motion of the hip in either group (p > 0.05).

Conclusion: Patients with noncontact ACL injury presented a greater alpha angle when compared with the group without tear. There was no difference in the rotational mobility of the hip between groups, nor was there a correlation between the increase in the alpha angle and the decrease in the rotational mobility of the hip.