Research on hip mechanics and knee pain

Some recent research in the British Journal of Sports Medicine on hip mechanics and their effect on knee kinematics and subsequent knee pain.  Academic rigour confirms what many clinicians had suspected in cases of PFPS. Hip kinematics play a large role in knee loading in the running athlete.

The effect of real-time gait retraining on hip kinematics, pain and function in subjects with patellofemoral pain syndrome

. Division of Physical Therapy, University of Kentucky, Lexington, Kentucky, USA
. 2 University of Delaware, Newark, Delaware, USA
. Correspondence to Dr Brian Noehren, Division of Physical Therapy, University of Kentucky, Wethington Bldg rm 204D, 900 S, Limestone Road, Lexington, KY 40536-0200, USA; bwn51{at}yahoo.com
Accepted 19 January 2010
Published Online First 28 June 2010

Abstract

Background Patellofemoral pain syndrome (PFPS) is the most common overuse injury in runners. Recent research suggests that hip mechanics play a role in the development of this syndrome. Currently, there are no treatments that directly address the atypical mechanics associated with this injury.

Objective The purpose of this study was to determine whether gait retraining using real-time feedback improves hip mechanics and reduces pain in subjects with PFPS.

Methods Ten runners with PFPS participated in this study. Real-time kinematic feedback of hip adduction (HADD) during stance was provided to the subjects as they ran on a treadmill. Subjects completed a total of eight training sessions. Feedback was gradually removed over the last four sessions. Variables of interest included peak HADD, hip internal rotation (HIR), contralateral pelvic drop, as well as pain on a verbal analogue scale and the lower-extremity function index. We also assessed HADD, HIR and contralateral pelvic drop during a single leg squat. Comparisons of variables of interest were made between the initial, final and 1-month follow-up visit.

Results Following the gait retraining, there was a significant reduction in HADD and contralateral pelvic drop while running. Although not statistically significant, HIR decreased by 23% following gait retraining. The 18% reduction in HADD during a single leg squat was very close to significant. There were also significant improvements in pain and function. Subjects were able to maintain their improvements in running mechanics, pain and function at a 1-month follow-up. An unexpected benefit of the retraining was an 18% and 20% reduction in instantaneous and average vertical load rates, respectively.

Conclusions Gait retraining in individuals with PFPS resulted in a significant improvement of hip mechanics that was associated with a reduction in pain and improvements in function. These results suggest that interventions for PFPS should focus on addressing the underlying mechanics associated with this injury. The reduction in vertical load rates may be protective for the knee and reduce the risk for other running-related injuries.