Gait retraining may prevent knee problems

The gait of runners whose kinematics place them at high risk for common running injuries and conditions may be retrained with the use of real-time feedback. Students in the University of Delaware's Biomechanics and Movement Science (BIOMS) program are conducting projects to determine how effective such retraining may be in preventing patellofemoral pain syndrome (PFPS), knee osteoarthritis (OA), and tibial fractures.

Gait retraining via real-time feedback relies on the use of 3-dimensional motion capture tools. Reflective markers are attached about the anatomy of a subject running on a treadmill. Marker movement is detected by a camera system that relays the subject's kinematic information to a computer, which maps the information as an animation on a monitor placed in front of the treadmill.

BIOMS PhD candidate Brian Noehren utilized real-time feedback in studying whether a retraining protocol could help runners who have PFPS-the most common running-related condition and one of the hardest to overcome. In an earlier study, Noehren found that PFPS is more likely to occur in persons who run with excessive hip adduction. His new study is designed to investigate the efficacy of real-time feedback gait retraining for reducing hip adduction, hip internal rotation, and pelvic drop in runners with PFPS. He also investigated whether the protocol could improve subjects' lower extremity functional index (LEFI) score, a measure of difficulty in performing activities of daily living.

In 8 sessions of gait retraining, subjects running on a treadmill received visual feedback on their hip angle in real time. They were instructed to contract their gluteal muscles to reduce hip adduction and move to keep a curve representing their hips within a region on the monitor that represents the range of normal hip adduction during stance.

Figure –A subject with patellofemoral pain syndrome is shown before (A) and after (B) retraining. Note the reduction in hip adduction, internal rotation, and pelvic drop.

The feedback protocol brought about significant reductions in hip adduction (25%), hip internal rotation (38%), pelvic drop (26%), and pain (a remarkable 97%), and the subjects experienced significant improvement in function (a 16% average increase in LEFI scores); the results held at 1-month follow-up (Figure). Long-term follow-up visits are planned to determine whether the changes persist for longer periods, thereby reducing the risk of PFPS recurrence.

Utting and associates¹ linked PFPS to the development of knee OA. The altered hip mechanics addressed in their study all are potential causes of OA in that they result in high-pressure compression of the patella.

Noehren suggests that modifications to the subjects' kinematics may translate into a reduction of PFPS recurrence and a decrease in the onset of OA. The significant decrease in pain and increase in function his subjects experience shows that real-time feedback has potential in treating runners with PFPS.

BIOMS postdoctoral fellow Joaquin A. Barrios, PT, DPT, PhD, is studying gait retraining and dynamic knee alignment. Varus-aligned persons tend to exhibit high knee adduction moments in their running gait. The adduction moments place a runner at risk for knee OA because they shift the load-bearing axis and, therefore, the gait-induced reaction forces to the inner region of the runner's knee. Barrios is investigating whether gait retraining could reduce knee adduction moments in varus-aligned persons.

In 8 sessions, the subjects were supplied with real-time kinematic feedback on their dynamic knee alignment. Extrinsic feedback was removed gradually using a faded feedback paradigm. Although subjects' natural gait was unchanged, all could execute the modified gait pattern on completion of the training series and at 1-month follow-up. The modified gait was associated with significant reductions in medial knee loading.

Overall, the subjects demonstrated a 10° increase in hip internal rotation and 3° increase in hip adduction. Knee adduction was decreased by 3°, and the knee adduction moment was decreased by 26%. Measurements of perceived effort and naturalness showed that the effort associated with the gait modification via real-time feedback is lower than that perceived by varus-aligned persons who have undergone other retraining protocols. Barrios suggested that the proposed modification, if reinforced and internalized systematically, could reduce the risk of knee OA.

Runners are at risk for stress fractures that result in short-term lapses in training, and they have a high reinjury rate. High loading at impact has been identified as a biomechanical risk factor for stress fractures because of both high tibial shock and high ground reaction forces. BIOMS graduate students Allison Altman, H. Philip Crowell, and Rebecca Fellin designed a study to determine whether a gait retraining protocol for tibial shock is effective in decreasing external impact loads and whether reduction of the external loads results in lower internal loads within the tibia.

Subjects ran on a customized, instrumented treadmill for 8 control sessions, followed by 8 retraining sessions. For the latter, an accelerometer was mounted on each subject's distal tibia to measure tibial shock. The subjects, provided with real-time feedback, were instructed to run "softer" and try to reduce their tibial shock. They achieved reductions in vertical loads (28%), tibial shock (41%), and internal tibial strain rate (15%) and maintained them at 1-month follow-up. The students are working on a 3-dimensional finite element model to use the strain rate data to determine whether a reduction in internal stresses is being achieved.

The BIOMS students are working under the guidance of Professor Irene Davis, PhD, PT, who has conducted numerous experiments aimed at understanding the relationships among lower extremity structure, mechanics, and injury. "The students' research represents an integration of experimental work with modeling," Dr Davis noted. "It offers insight into the causes of these serious overuse problems and provides a novel intervention for patients."

References:

1. Utting MR, Davies G, Newman JH. Is anterior knee pain a predisposing factor to patellofemoral osteoarthritis? Knee. 2005;12:362-365.