Altered Hip and Trunk Muscle Function in Those with Patellofemoral Pain Syndrome

Research Review: Altered Hip and Trunk Muscle Function in Those with Patellofemoral Pain Syndrome

By Tristan Rodik, M. AT., ATC

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

Original Citation: Cowan, S. M., Crossley, K. M. and Bennell, K. L. (2009) Altered hip and trunk muscle function in individuals with patellofemoral pain. British Journal of Sports Medicine, 43, 584-588 Abstract

Introduction: Patellofemoral pain syndrome (PFPS) is a common injury that may result from inhibited hip and quadriceps muscle function (1-15). This 2009 study, conducted in Australia, investigated gluteus medius strength and activation, lateral core strength, and hip rotation range of motion in participants with and without PFPS. The findings demonstrate that individuals with PFPS have decreased lateral core strength and delayed activation of the gluteus medius and vastus medialis oblique when performing a step-up test. Human movement professionals may consider adding assessments and techniques to their repretiore, for addressing these impairments.

Caption: Knee Pain Referral Pattern

Knee Pain Referral Pattern

Study Summary

Study Design	Cross-sectional, observational design
Level of Evidence	III Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies, and case-control studies
Subject Characteristics	Demographics: Patellofemoral Pain Syndrome (PFPS) Group Number of participants: 10 Age: 26 +/- 10.1 Height: 1.72 +/- 0.04 cm Weight: 63 +/- 8 kg Gender: 3 men, 7 women Demographics: Control Group Number of participants: 27 Age: 25.4 +/- 5.5 Height: 1.9 +/-0.09 cm Weight: 69 +/- 9 kg Gender: 12 men, 15 women Inclusion Criteria (PFPS Group): Anterior or retro-patellar knee pain during at least two of the following activities: prolonged sitting climbing stairs squatting running kneeling hopping or jumping Symptoms for at least 1 month Average pain of 3/10 on the visual analog scale Insidious onset of symptoms 40 years old or younger, to reduce the likelihood of osteoarthritis Inclusion Criteria: Control Group Asymptomatic at the time of testing Exclusion Criteria (PFPS): Signs of other lower-extremity pathologies Knee surgery within the previous 3 months History of patellar dislocation/subluxation Clinical evidence of meniscal injury Ligamentous instability Traction apophysitis around the patellofemoral complex Patellar tendinopathy Chondral damage Spinal radiculopathy Exclusion (Control Group): History of lower-limb pathology Current health condition that may effect kinetic or kinematic hip and/or knee movement
Methodology	Electromyographic (EMG) Analysis EMG analysis was carried out on the following muscle groups: Vastus medialis oblique (VMO) Vastus lateralis (VL) Anterior gluteus medius Posterior gluteus medius Surface electrodes were used for the VMO, VL and anterior gluteus medius. Intramuscular electrodes were used for the posterior gluteus medius. Self-reported Pain Rating Participants rated their pain on a 10cm numerical scale Stepping Task A box 22cm in height was used for a step-up task. Different colored lights were shown indicating which leg, right or left, would be used to step-up Participants were instructed to step-up as quickly as possible once the color was shown The step up was performed five times on each leg, for a total of 10-repetitions Only the effected extremity for each PFPS participant was analyzed Hip Rotation Range of Motion (HRROM) A gravity inclinometer placed along the fibula was used for measurement Participants were in a supine position with neutral hip alignment HRROM was measured as participants rotated the tested extremity internally and externally Hip External Rotation Strength Two warm-up trials were followed by 3 tested trials Participants were in a seated position The dynamometer was placed along the tibia Hip Abduction Strength Two warm-up trials were followed by 3 tested trials Participants were in a supine position and abducted their leg with maximal effort The dynamometer was placed along the fibula Lateral Core Strength Two warm-up trials were followed by 3 tested trials Participants assumed a side-plank position The dynamometer was placed proximal to the greater trochanter
Data Collection and Analysis	EMG Ag/AgCl surface electrodes (Graphics Control Corporation, c/o Medical Equipment Services Pty Ltd, Richmond, Australia) EMG intramuscular electrodes (AM Systems, Carlsborg, Western Australia) Intramuscular electrodes were inserted with ultrasound guidance (7.5 MHz curved linear array transducer; Dornier Performa, Acoustic Imagine Technologies Corp, Phoenix, USA) EMG data was sampled at 2000 Hz, bandpass filtered between 20 and 1000 Hz using a Power1401 data acquisition system and Spike5 software (Cambridge Electronic Design, Cambridge, UK) and analyzed using IGOR Pro (Igor Pro 5, Wavemetrics, Inc, Lake Oswego, Oregon, USA) A force plate was used during the stepping task (Kistler, Switzerland, model 9286AA (400 x 600 mm) software: Bioware version 3.21)
Outcome Measures	Unpaired t-tests were used to compare the following (between groups): muscle activation onset muscle activation peak step-up reaction time force plate variables hip range of motion strength measures Independent one group t-tests were used to determine if muscle onset differed significantly from zero Significance was set to a p value of 0.05
Results	Descriptive Characteristics PFPS group participants had an average pain level of 4 and experienced pain for an average of 6 months The dominant limb was the painful limb in 50% of the participants Control Group (Performing the Step-up Task) The onset of the anterior and posterior gluteus medius occurred before heel strike only the anterior gluteus medius onset was significant (p = 0.01) VL and VMO onset occurred simultaneously (p = 0.00) PFPS Group (Performing the Step-up Task) Anterior and posterior portions of gluteus medius activation were delayed when compared to the control group (p = 0.01 and p = 0.012, respectively). Although not significant, anterior and posterior gluteus medius activation onset occurred after heel strike VMO onset was delayed which contributes to discrepancies in VL and VMO activation when compared to the control group (p = 0.001). Strength Testing No significant differences were noted between groups regarding hip abduction strength nor external rotation strength (p = 0.39 and p =0.77, respectively) The PFPS group had significantly less (29%) lateral core strength compared to the control group (p = 0.033) Hip Rotation Range of Motion (HRROM) No significant differences occurred between internal nor external rotation range of motion (p = 0.88 and p = 0.96, respectively)
Our Conclusions	This study identified weakness in lateral core strength and delayed gluteus medius and VMO activity in individuals with PFPS. The findings of this study are congruent with the model and intervention described in Lower-Extremity Dysfunction (LED).
Researchers' Conclusions	This study found significantly decreased lateral core strength in the PFPS group compared to the control group. The PFPS group demonstrated delayed gluteus medius and VMO activation during the step-up task. Hip rotation range of motion values did not vary among groups.

Caption: Knee Joint Anterior to Posterior Mobilization

Knee Joint Anterior to Posterior Mobilization

How this Study Contributes to the Body of Research:

This study further contributes to a growing body of research regarding patellofemoral pain syndrome (PFPS) and activity of the gluteus medius , gluteus maximus , vastus lateralis , and vastus medialis (1-15). Relatively unique to this study, recruitment timing was measured in conjunction with electromyographic (EMG) data, revealing delays in the activation of the gluteus medius . Further, this study included EMG analysis of the glute complex , the vastus medialis oblique (VMO) vastus lateralis, lateral core muscle strength, and hip rotation range of motion. The inclusion of peak activity and timing of multiple muscles, along with range of motion aids in aggregating trends noted in other studies, allowing for a more complete understanding of the impairments that develop in this group.

How the Findings Apply to Practice:

This study revealed reduced lateral core strength and delayed gluteus medius and vastus medialis oblique (VMO) activation during a step-up task in individuals with PFPS. It should be noted that the side plank used for lateral core strength assessment could also be affected by gluteus medius strength. Human movement professionals should add assessments and interventions for these impairments to the evaluation and treatment of PFPS.

This study had many methodological strengths, including:

Researchers were blinded to data and participant group assignment, diminishing the potential for observer bias.
The step-up task , hip abduction , and lateral strength testing used in the study are easily replicable in practice.
The rapid decision making that participants were required to make as part of the step-up task helped reduce the possibility that participants prepared for the movement.

Weaknesses that should be noted prior to clinical integration:

A small cohort of 10 participants made up the PFPS group, reducing the generalizability to a wider population.
Although range of motion (ROM) was not significantly different between groups, the position used to assess ROM was unusual and has not been established within current literature as reliable nor valid.
Muscle activation was not represented as a percentage of maximum voluntary isometric contraction, making it difficult to compare findings across other studies focused on the same muscle groups.

How This Study Relates to Brookbush Institute Content:

The study findings are congruent with The Brookbush Institute's (BI) predictive models of Lower-Extremity Dysfunction (LED), Lumbo Pelvic Hip Complex Dysfunction (LPHCD) , and Sacroiliac Joint Dysfunction (SIJD) . An integrated approach is recommended for the assessment and intervention of PFPS. The Brookbush Institute recommends dynamic postural assessment , manual muscle testing , and range of motion assessment similar to those used in the study; however, BI has not recommended specific assessment of lateral core strength. More consideration will be needed to determine practicality, reliability, and effect on intervention selection of this test. Gluteus medius activation and vastus medialis oblique (VMO) activation are commonly recommended for individuals with PFPS.

Sample Videos Related to the Research Study Content:

Gluteus Medius Manual Muscle Testing (MMT) for an Active Population

Isolated Activation of the Gluteus Medius

Vastus Medialis Obliques Activation Progressions:

Side-Stepping Progressions for Gluteus Medius Reactive Activation

Side-Plank Progressions

Bibliography:

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