Editorial Commentary: The Hip Bone's Connected to the Knee Bone, but Correlation Does Not Equal Causation—The Association of Hip Motion, Femoroacetabular Impingement, and Anterior Cruciate Ligament Injury

Abstract

Patients with anterior cruciate ligament (ACL) injury had significantly less hip rotational motion (internal rotation [IR] and sum of IR and external rotation) than control subjects without ACL tears. For each hip IR increase of 10°, the odds of sustaining an ACL rupture decreased by a factor of 0.419. Although this investigation does not prove (causation) that loss of hip rotational motion causes an ACL tear, it does continue to complement the growing and evolving literature base showing an upstream or downstream association (correlation) of decreased hip motion on adjacent structures.

Editorial Commentary: I Have a Hip Labral Tear? Well, That Makes Sense Because I Had a Labral Tear in My Shoulder Too

“…4 It is also well known that hip pathomorphology can have a significant biomechanical impact both upstream and downstream (lumbosacral spine, periarticular hip musculature, knee [anterior cruciate ligament], and shoulder and elbow). [5][6][7][8] This makes the study "High Prevalence of Concomitant Shoulder Labral Tears in Patients With Femoroacetabular Impingement" by Vahedi, Fleischman, Salvo, and Parvizi 9 important as they attempt to determine whether an association exists between hip and shoulder labral tears.…”

“…The use of a "control" group such as ACLR patients is slightly biased because there may be a relation between cam morphology, loss of hip motion, and ACL tears. 6,22 However, such a bias, if anything, would cause the results to underestimate a difference compared with a cam group, because there is a higher rate of cam morphology observed in subjects with ACL tears. The acquisition of a shoulder "labral tear" could imply a labral injury anywhere on the labrumdSLAP, posterior tear, or anterior tear.…”