Hip Torque in Individuals With and Without Knee Pain

Research Review: Hip Torque in Individuals With and Without Knee Pain

By Erik Korzen DC

Edited by Brent Brookbush DPT, PT, COMT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Boling, M.C., Padua, D.A., Creighton, R.A. (2009). Concentric and eccentric torque of the hip musculature in individuals with and without patellofemoral pain. Journal of Athletic Training, 44(1), 7-13. Full Article

Why is this relevant?: Patellofemoral pain (PFP) is a common condition among an active population. Several studies have reported a correlation between PFP and changes in hip motion and motor recruitment (1-4). This study examined the differences in concentric and eccentric strength of hip extensors, external rotators and abductors in subjects with and without PFP. This study indicates that concentric and eccentric hip torque production in the transverse and frontal plane may lead to changes in femoral positioning related to PFP. The findings of this study may imply changes in intervention strategies related to knee pathomechanics and pain, specifically PFP.

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Study Summary

Study Design	Case Control Study
Level of Evidence	VI - Evidence from a single descriptive or qualitative study
Subject Demographics	20 subjects with patellofemoral pain (PFP) & 20 subjects without PFP (control) were recruited from the student/faculty/staff population of a university Age: PFP group: 26.8 years +/- 4.5 Control group: 25.6 years +/- 2.8 Gender: 7 males and 13 females in both PFP and Control groups Inclusion Criteria: PFP group - anterior/retropatellar knee pain present during at least 2 of the following activities: ascending/descending stairs, hopping or running, squatting, kneeling and prolonged sitting; insidious onset not related to trauma; pain on palpation of patellar facets; worst pain in past week greater than or equal to 3cm on 10cm on a visual analog scale (VAS). Exclusion Criteria: PFP and Control groups - history of knee surgery; clinical evidence of other knee injury; current significant injury affecting other lower extremity joints
Outcome Measures	Visual Analog Scale (VAS), 0cm-10cm with 10cm indicating the most severe pain Anterior Knee Pain Scale (AKPS) questionnaire, 100 is highest possible score indicating better perceived function. Average and Peak Concentric and Eccentric Torque of: Hip Extensors Hip Abductors Hip External Rotators Participants performed 5 repetitions of each strength test using an isokinetic dynamometer. All strength testing was performed at 60°/second, allowing for optimal assessment of both concentric and eccentric force-producing capacity. Hip extension was measured using a machine, with the participant lying prone and the axis of rotation aligned with the greater trochanter. Hip extension was performed from 60° and 90° of hip flexion to end range. Hip abduction was measured with the participant lying on their side, with the non-test leg stabilized with straps. The axis of rotation was aligned medial to the anterior superior iliac spine (ASIS) at the level of the greater trochanter. This was performed from 0° to 20° of hip abduction. Hip external rotation was measured with the participant seated and the hip and knee flexed to 90°. The axis of rotation was aligned with the joint line of the knee. This test was performed through a range of 5° of hip internal rotation to 20° of hip external rotation. Peak and average torque data for concentric and eccentric was collected. The average of the middle 3 trials was used for data analysis to account for learning (trial 1) and fatigue (trial 5).
Results	The PFP group did not significantly differ from control group on measures of age, height, or mass VAS results PFP: 5.06 +/- 2.27cm Control: 0.14 +/- 0.28cm AKPS results PFP: 68.90 +/- 9.15 Control: 99.10 +/- 2.73 Torque Results PFP group: Weaker Hip Abduction peak eccentric torque PFP group: Weaker Hip External Rotation average concentric and eccentric torque PFP and Control groups were NOT significantly different for Hip Extension torque
Conclusions	Participants with PFP were an average of 21% weaker than the pain free controls for peak eccentric hip abduction torque and 23% weaker for both average concentric and eccentric hip external rotation torque.
Conclusions of the Researchers	When compared to pain-free controls, subjects with PFP demonstrated reduced peak eccentric hip abduction torque and average concentric and eccentric hip external rotation torque.

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Review & Commentary:

There were many strong components to the methodology of this research. The authors obtained matched control and PFP groups for age, height and mass. The authors utilized previously researched methods for isometric strength testing of the hip extensors, abductors and external rotators. The researchers used the middle 3 trials of the strength tests for data analysis to reduce the effects of learning and fatigue. While the researchers were not blinded to the group assignments, the subjects order of strength testing was randomized and they were provided 2 minutes of rest between testing, reducing the chance that order of testing influenced results.

In previous research the method most commonly used for assessing strength has been isometric testing. The inclusion of eccentric and concentric torque testing provided additional information that may influence intervention selection related to PFP and the hip musculature. A single study may not be enough to establish certainty that hip musculature torque has a causative relationship with PFP, but this study adds to a growing body of research associating weakness of hip musculature and PFP. This includes a study by [Ireland et. al (4),](http://Ireland, ML., Wilson, JD., Ballantyne, BT., Davis, IM. (2003). Hip Strength in Females With and Without Patellofemoral Pain. J Orthop Sports Phys Ther 2003. 33: 671-676.) that reported similar findings regarding eccentric hip abduction torque.

This research also had limitations. While the use of the isokinetic dynamometer provided a great deal of raw data; however, the range of motions tested and the body position used may lead to questions regarding the carryover of study results to functional tasks. Additionally, it would have been beneficial if the authors could have included a pain questionnaire pre- and post-testing to determine if the concentric or eccentric use of certain hip muscles had an effect on subjects with PFP. Last, considering the participant positioning and equipment used, minor variations in position and direction of force (relative to the hip) may have occurred that would have resulted in changes in muscle recruitment that could have altered data.

Why is this study important?

This study provides evidence to support the concept of regional interdependence between the hip and knee. It also indicates that concentric and especially eccentric strength of hip external rotators and abductors may contribute to change in knee mechanics that lead to pain. Surprisingly, no changes were found in hip extensor strength. This may imply that focus should be placed on both concentric and eccentric strength of external rotators and abductors, and less focus placed on extension. Further, this research highlights that isometric strength testing may not be sufficient for assessing changes in muscle function relative to pain.

How does it affect practice?

While it is important to assess the painful or dysfunctional segment using typical evaluation techniques, this research supports the use of multiple strength assessments of proximal and distal joints related to the site of pain. Further, the sole use of isometric strength testing does not provide a full picture of dysfunction, and dynamic movement screens should be added to assess the concentric and eccentric function of muscles recruited. This research may also imply the use of exercises for proximal and distal joints and their related musculature. The individuals with PFP in this study demonstrated weakness in eccentric hip abduction and hip external rotation, suggesting that activation and integration of the gluteus medius and gluteus maximus may provide benefit for those experiencing knee pain.

How does it relate to Brookbush Institute Content?

The changes in concentric and eccentric external rotator and abductor strength, closely resembles the joint dysfunction and muscle imbalances described in the predictive models of postural dysfunction - Lower Leg Dysfunction (LLD) and Lumbopelvic Hip Complex Dysfunction (LPHD) . Further, the corrective exercise intervention recommended based on these models include gluteus maximus activation, gluteus medius activation, as well as the deep rotators of the hip; muscles that would contribute to external rotator and abduction strength. The Overhead Squat Assessment is a useful identify signs relating to both of these dysfunctions, especially the sign, "Knees Bow In".

The videos below describe the "Knees Bow In" sign, as well sample corrective interventions for gluteus medius and gluteus maximus weakness.

Overhead Squat Assessment: Knees Bow In

Quick Glute Activation Circuit:

Glute Reactive Activation:

Glute Complex Kinesiology Taping:

Questions, comments, and criticisms are welcomed and encouraged -

Hip Torque in Individuals With and Without Knee Pain

Research Review: Hip Torque in Individuals With and Without Knee Pain

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