Posterior Hip Mobilizations in Resting Position May Not Be Enough to Improve End-Range Hip Flexion Range of Motion

Research Review: Posterior Hip Mobilizations in Resting Position May Not Be Enough to Improve End-Range Hip Flexion Range of Motion

By Nicholas Rolnick SPT, MS, CSCS

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

Original Citation: Loubert, P. V., Zipple, J. T., Klobucher, M. J., Marquardt, E. D., & Opolka, M. J. (2013). In vivo ultrasound measurement of posterior femoral glide during hip joint mobilization in healthy college students. journal of orthopaedic & sports physical therapy, 43(8), 534-541. ABSTRACT

Why the Study Is Relevant: Human movement professionals perform hip joint mobilizations to improve range of motion and/or reduce pain. It is hypothesized that these improvements are due to the restoration of accessory joint motion (arthrokinematics) (1). This 2013 study from Central Michigan University suggests that if arthrokinematic dysfunction of the hip joint is suspected, hip mobilizations will be optimized if performed in the restricted ranges of motion (as opposed to resting position).

The Brookbush Institute recommends posterior-to-anterior self-administered hip joint mobilizations for individuals with suspected arthrokinematic dysfunction.

Caption: The Brookbush Institute recommends posterior-to-anterior self-administered hip joint mobilizations for individuals with suspected arthrokinematic dysfunction.

The Brookbush Institute recommends self-administered posterior-to-anterior hip joint mobilizations for individuals in whom arthrokinematic dysfunction is suspected.

Study Summary

Design	Descriptive Study
Level of Evidence	Level III - Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies, and case-control studies.Shekelle, P. G., Woolf, S. H., Eccles, M., & Grimshaw, J. (1999). Developing clinical guidelines. Western Journal of Medicine, 170(6), 348.
Characteristics of the Subjects Characteristics of the Investigator and Recorder Definitions Methodology	Characteristics: Number: 20 Age (in years) - 24.3 ± 1.7 Body mass index (in kg/m²) - 23.4 ± 2.8 Gender: N/A Height (in cm) (Standard deviation) - 172.6 ± 9.9 Weight (in kg) - 69.9 ± 12.5 Tissue depth (in cm) - 2.7 ± 0.5 Hip Mobilized: Right 14; Left; 16 The investigator doing the mobilizations had a manual therapy certification and 25 years of clinical experience. A graduate student researcher, trained by the faculty members of the research team, monitored and supervised the transducer during image acquisition. Translational glide: Joint play, a component of accessory joint mobility known as arthrokinematics. Occurs when one articular surface glides over the other in a linear or curvilinear direction with no change in the angle between the bones or articular surfaces forming the joint. Calculated using the formula: Tangential glide = 2πr(ROM/360°) where r = radius of the femoral head and ROM is the range of motion of hip flexion of each subject Tangential glide: When the angular displacement of the bones and their corresponding articular surfaces change; associated with osteokinematic motion but is necessary for arthrokinematic motion as well; commonly called a roll slide* or roll glide. Pre-Test The hip to be mobilized was randomly assigned for all subjects. ROM testing in flexion, extension, abduction, adduction, internal rotation, and external rotation with a goniometer was performed on the selected hip according to standard practice. ROM values were compared to published norms to ensure that the subjects exhibited no gross deficits in ROM. Subject Positioning Each subject was supine on a force plate. The selected hip was put in its resting position (approximately 30° of flexion, 30° of abduction and neutral rotation), with the other leg resting on a wood box. Towels were placed on the hip to ensure proper positioning throughout the testing procedure. Cuff weights were positioned behind the iliac crests, along with a belt slightly inferior to the anterior superior iliac spines to stabilize the pelvis of each subject. Subjects were told to report pain or discomfort so their positioning could be adjusted during the experiment. Ultrasound Imaging An ultrasound transducer was oriented vertically to allow for visualization of an anterior/posterior image of the femoral head in the transverse plane. The transducer was translated medially and laterally until the femoral head was centered in the field of view and a picture was taken. With the transducer still in place, a line was drawn on the subject outlining the transducer. A second line was drawn perpendicular to and extending from the midpoint, of the first line. Both lines facilitated analysis of the femoral head translation during the mobilizations. Mobilizations The subject was asked to relax, and a posteriorly-directed mobilization force through the femur was administered perpendicular to the force plate at 50% of the subject's body weight. Once the target force was attained, a second ultrasound image was taken and the mobilization was stopped so the hip could return to the resting position. The procedure was repeated 12 times on each subject, for 24 images (1 pre- and 1 post-mobilization) for each subject. Measuring the Degree of Slide Post-image processing was performed on the ultrasound machine after the intervention concluded. Multiple observer consensus determined the location of endpoints for measurements. Femoroacetabular distance was defined as the linear distance between the superiormost point of the acetabulum and the superiormost point of the femoral head as they appeared on the ultrasound display. A horizontal line was drawn intersecting the uppermost point of the acetabulum. A vertical line was drawn perpendicular to the horizontal line beginning at the uppermost point of the femoral head. The length of this line was defined as the femoracetabular distance. The difference between the resting and mobilization femoracetabular distances was the amplitude of translational glide for each trial. The three trials that had the greatest amplitude of differences within 0.5 mm of each other were averaged, and used for data analysis. The image of each subject's femoral head was exported to a computer-aided design program to determine the radius of the femoral head. A circle was drawn to superimpose the image of the femoral head, and then the radius of the circle was measured to calculate the full glide needed to achieve full hip flexion range of motion. A ratio of translational glide, tangential glide was calculated to provide an estimate to the amount of ROM that a posterior mobilization might influence. Correlations were calculated for glide amplitude vs. mobilization force and glide amplitude vs. femoral head diameter to determine if body-mass scaling of mobilization forces was adequate for between-subject comparisons of different body sizes. Inclusion Criteria: N/A Exclusion Criteria: Pregnancy Previous or current musculoskeletal condition that could affect hip, low back, and/or pelvis
Outcome Measures	Hip Flexion ROM for Each Subject Femoral Head Radius (in mm) Posterior Translational Glide (for Each Subject), in mm Calculated Tangential Glide (for Each Subject), in mm Translational Glide-Tangential Glide Ratio, in %
Results	Note: Twenty of the 240 trials were excluded from data analysis because one or both of the images were not sufficient to measure. Average posterior femoral glide was 2.00 mm (0.8-4.2 mm range) No significant association between posterior femoral glide amplitude and mobilization force (r = 0.27, p = 0.26) or between posterior femoral glide amplitude and femoral head diameter (r = 0.07, P = 0.76) Average tangential glide for all subjects was 53.88 mm (43.2-64.8 mm range) Average tangential glide as a percentage of calculated tangential glide was 3.8% (1.5-7.9%)
Our Conclusions	Hip mobilizations in the resting position will do little to improve ROM restrictions into hip flexion. To increase the intervention's efficiency, mobilizations near end-range hip flexion should be performed.
Researchers' Conclusions	Posterior hip mobilizations in the resting position do not produce enough translational glide to assist in restoring hip flexion range of motion based on the total amount of tangential glide required. Therefore, translational restrictions may not be a significant part of arthrokinematic dysfunction of the hip joint. Mobilization in the resting position of the hip may only restore a small portion of the hip ROM closest to the area of intervention.

Caption: Hip flexion goniometry is one assessment tool needed in order to determine if a posterior hip mobilization is indicated.

Hip flexion goniometry is one assessment tool needed in order to determine if a posterior hip mobilization is indicated.

Review & Commentary:

The study was one of the first to use ultrasound technology to quantify the degree of femoral head translation during a posterior hip mobilization performed in the resting position. It provides important information on how joint architecture influences arthrokinematics. Normal arthrokinematic motion consists of combinations of rolls and glides, and it is primarily determined by the congruency of the joint surfaces (2). Unlike the shoulder , the hip is a ball-and-socket joint with a high degree of congruence; in theory, this should limit the degree of glide available during arthrokinematic assessment. Although in vivo investigations have not yet tested this hypothesis, posterior hip mobilizations are frequently used to improve hip flexion range of motion . This study used ultrasound to measure the degree of translational glide (slide) during a posterior hip mobilization in the resting position. The results indicate very little translational glide in the hip (only ~3.8% required for full range of hip flexion).

The study had many methodological strengths, including:

There was a clear description of the protocol, allowing for replication of the study, perhaps investigating other commonly used mobilizations (such as inferior, lateral, or anterior hip mobilizations ).
This study demonstrates a high degree of clinical relevancy, as posterior hip mobilizations are frequently performed in rehabilitation and performance settings. This study was also one of the first to scale the applied mobilization force used in the intervention to each subject's body mass, increasing clinical relevancy.
This study made great use of technology (ultrasound and computer-aided software) to minimize measurement error. The authors reduced any errors in placement of the ultrasound transducer among trials by marking the placement on each subject.
This study bridged a gap in the literature; no other study has quantified the degree of femoral head translation using ultrasound technology in a posteriorly directed hip mobilization with a force scaled to each subject's body mass. Important clinical implications are discussed below.

Weaknesses that should be noted prior to clinical integration of the findings include:

Muscle guarding was not discussed or considered, but may significantly limit passive joint assessment (3). Future studies should employ electromyography to monitor muscle activity.
The researchers did not include any post-intervention data such as hip range of motion and/or pain. The authors noted that the effects would be minimal, considering the population and the acute nature of the mobilization force. However, future research should investigate the effects of hip mobilizations on clinically important outcome measures in healthy and pathologic populations.
The subjects were young and healthy, with no history of hip dysfunction . Caution should be taken in extrapolating the results of this study to other populations, especially in those with articular dysfunctions. Future research should be done on individuals with known hip pathologies.

Why This Study Is Important

Human movement professionals should consider the architecture of the joint they are attempting to mobilize, as it could have a significant impact the effectiveness of the mobilization. The findings support the theory that the architectural morphology of the hip joint restricts translational mobility of the femoral head. Posterior hip mobilizations in the resting position do not produce enough movement to replicate the amount required for normal hip flexion (only about ~3.8% required). Due to the limited translational movement of the femur during this mobilization and the amount needed to improve range of motion, performance of this technique in the resting position is not advised.

How the Findings Apply to Practice

Hip mobilizations performed in the resting position do not produce enough femoral head motion to be clinically effective for improving range of motion. In order to improve the technique's effectiveness, human movement professionals should mobilize in or near the restricted range of motion (i.e. end-range flexion). Additionally, as tangential motion of the hip is limited at end-range, adding active or passive hip flexion may improve clinical outcomes.

Related Content From Brookbush Institute

Restrictions in hip flexion range of motion occur in individuals with lumbopelvic hip complex dysfunction and lower leg dysfunction . The Brookbush Institute (BI) advises using joint mobilizations when muscular interventions (such as foam rolling, release techniques, stretching ) are not effective. Limitations are typically a result of a tight posterior capsule and ligaments, which produce excessive superior and anterior glide of the femur in the acetabulum. Human movement professionals whose scope of practice includes manual therapy, should use posterior hip mobilizations to improve the extensibility of the capsule and restore optimal arthrokinematic function. Additional manual therapy content, including hip joint mobilizations, will be forthcoming.

Human movement professionals can accomplish similar goals with their clients through self-administered hip joint mobilizations .

The results of the current study align with the BI's view that joint mobilization intervention is joint/dysfunction specific. As the hip joint does not permit much translational movement, mobilization and treatment in the resting position to improve range of motion is not recommended. The most effective interventions to address arthrokinematic dyskinesis of the hip should be performed near the range of motion restriction, with some active or passive component.

The following videos illustrate common assessment techniques and interventions used to treat hip flexion range of motion restrictions and lumbopelvic hip complex dysfunction .

Brookbush Institute Videos

Overhead Squat Assessment: Anterior Pelvic Tilt

Modified Thomas Test

Hip Flexion Goniometry

Self-Administered Anterior-to-Posterior Hip Joint (with Flexion) Mobilization

Self-administered Lateral Distraction Mobilization in Quadruped

Bibliography:

International Maitland Teachers association. A tribute to the life and work of G.D.Maitland 1924-2010. Manual Therapy. 2010; 300-30
Grosland NM, Rogge RD, Adams BD. Influence of articular geometry on prosthetic wrist stability. Clin Orthop Relat Res. 2004; 134-142.
Dhayer YY, Tsoumanis AD, Houle TT, Rymer WZ. Neuromuscular reflexes contribute to knee stiffness during valgus loading. J Neurophysiol. 2005; 93: 2698-2709.

Additional Information Regarding The Study's Methodology:

The equation "2πr*(ROM/360°)" was used to calculate the amount of tangential glide required for full hip flexion range of motion in each subject. An important assumption made in this equation is complete sphericity of the femoral head. To avoid violating the assumption of the equation, the authors checked femoral head sphericity with computer-aided imaging for each subject. Due to the high degree of inherent sphericity of the femoral head, the authors concluded that any variations in femoral head shape between subjects would matter little in influencing tangential glide, as the femoral head was nearly completely spherical in all subjects.

Questions, comments and criticisms are welcomed and encouraged -

Posterior Hip Mobilizations in Resting Position May Not Be Enough to Improve End-Range Hip Flexion Range of Motion

Research Review: Posterior Hip Mobilizations in Resting Position May Not Be Enough to Improve End-Range Hip Flexion Range of Motion

Brookbush Institute Videos

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