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Tuesday, June 6, 2023

Outcomes of Functional Training Compared to Quadricep Strengthening in Females with Patellofemoral Pain Syndrome

Brent Brookbush

Brent Brookbush


Research Review: Functional Training Intervention Compared to Quadricep Strengthening Intervention in Women with Patellofemoral Pain Syndrome.

By Tristan J. Rodik M.AT., ATC

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

Original Citation: Baldon, R. D. M., Serrao, F. V., Silva, R. S. and Piva S. R. (2014) Effects of functional stabilization training on pain, function, and lower extremity biomechanics in women with patellofemoral pain: a randomized clinical trial. Journal of Orthopaedic and Sports Physical Therapy, 44(4), 240-A8. Full Article

Why the Study is Relevant: Patellofemoral pain syndrome (PFPS) is a common diagnosis among active populations, especially female athletes (1, 2). Prior research has demonstrated that females with PFPS often present with decreased hip abductor and external rotator strength (3-9), abductor strengthening has been shown to aid in the resolution of dysfunction (10), however, many professionals treat PFPS with quadriceps strengthening. This 2014 study by Baldon et al. demonstrated that hip strengthening and verbal feedback for trunk and pelvic control was superior to quadriceps strengthening for reducing pain and improving function in females with PFPS.

3 Images of individuals with a functional knee valgus - excessive femoral internal rotation and adduction.
Caption: 3 Images of individuals with a functional knee valgus - excessive femoral internal rotation and adduction.

Images of "Functional Knee Valgus" - Excessive adduction and internal rotation of the hip as a result of weak hip abductors and poor pelvic and trunk control. (Courtesy of the Brookbush Institute©)

Study Summary

Study DesignRandomized controlled trial
Level of EvidenceIB Evidence from at least one randomized controlled trial
Participant CharacteristicsDemographics
  • Age: 18-30
  • Gender: female
  • Number of participants: 31

Functional Stability Training Group

  • Age: 22.7 +/- 3.2
  • Height: 1.66 +/- 0.1 meters
  • Mass: 57.1 +/- 8.2 kilograms
  • Body Mass Index: 20.6 +/- 2.0
  • Symptom Duration: 60 (3-156) months
  • Number of Participants: 15

Standardized Training Group

  • Age: 21.3 +/- 2.6
  • Height: 1.6 +/- 0.1 meters
  • Mass: 58.3 +/- 7.3 kilograms
  • Body Mass Index: 22.3 +/- 2.5
  • Symptom Duration: 27 (3-180) months
  • Number of Participants: 16

Inclusion Criteria:

  • Female
  • 30 minutes of aerobic or athletic activity at least 3x/week
  • Anterior knee pain of 3 or greater on 10-cm Visual Analog Scale (VAS) for a minimum of 8 weeks
  • Anterior or retropatellar knee pain with at least 3 of the following activities:
    • ascending/descending stairs
    • squatting
    • running
    • kneeling
    • jumping
    • prolonged sitting

  • Gradual onset of symptoms unrelated to trauma

Exclusion Criteria:

  • Intra-articular pathology
  • Cruciate or collateral ligament injury
  • Patellar instability
  • Osgood-Schlatter or Singding-Larsen-Johansson syndrome
  • Hip pain
  • Knee joint effusion
  • Previous lower-limb surgery
  • Tenderness upon palpation of the patellar tendon, iliotibial band or pes anserinus tendons.
  • Participants were randomly assigned to the functional stabilization training (FST) group or the standardized training (ST) group
  • Measures were recorded at baseline, intervention completion (2-months) and 3-months post-intervention:
    • Baseline: VAS, lower extremity functional scale (LEFS), single-leg triple hop (SLTH), kinematic testing, trunk endurance and strength testing
    • Intervention completion: VAS, LEFS,  SLTH, Kinematic Testing, trunk endurance and strength testing
    • 3-months post-intervention: VAS, LEFS and global rating of change

  • The LEFS is a 20-item questionnaire that rates participants' difficulty performing functional tasks
  • To perform the SLTH for distance, participants jumped 3 consecutive times on one leg; total distance was tracked for each participant
  • The VAS is a 10-cm scale rating participants pain from 'no pain' (0) to 'worst pain imaginable' (10).
  • The global rating of change scale measures participants' perception of their improvement throughout an exercise intervention
  • Kinematic testing using the single leg squat evaluated the following parameters:
    • Trunk ipsilateral/contralateral inclination
    • Pelvis contralateral elevation/depression
    • Hip abduction/adduction
    • Knee abduction/adduction
    • Trunk flexion/extension
    • Pelvis anteversion/retroversion
    • Hip flexion/extension

  • Trunk muscle endurance was tested for the back extensors, abdominals and oblique musculature.
  • Eccentric strength was tested using an isokinetic dynamometer for the following muscles:


  • The ST group performed stretching and traditional quadricep strengthening exercises
  • The FST group participated in 3 phases of intervention:
    • Phase 1 (2 weeks): enhance motor control of the trunk and hip muscles
    • Phase 2 (3 weeks): improve trunk and hip muscle motor control and strength. Participants were also educated on lower-limb alignment and its effect on knee pain.
    • Phase 3 (3 weeks): exercises were progressed and participants were consistently educated on lower-limb alignment

  • Exercise intervention began 3-5 days after baseline testing
  • Both groups performed their intervention 3x/week for 8 weeks under the supervision of a physical therapist
  • Participants progressed exercises when they could be performed without exacerbating pain, excessive fatigue and/or local muscle pain after training.
Data Collection and Analysis
  • Kinematic testing was assessed with the Flock Birds electromagnetic tracking system (miniBIRD; Ascension Technology Corporation, Shelburne, VT) and MotionMonitor Software (Innovative Sports Training, Inc, Chicago, IL)
  • Kinematic data was filtered using a fourth-order, zero-lag, low-pass Butterworth filter at 6Hz
  • Biodex Multi-Joint System 2; Biodex Medical Systems, Inc, Shirley, NY
  • Outcome measures were assessed using a repeated-measures analysis of variance.
  • LEFS and SLTH were analyzed with a 2-by-3 analysis of variance
  • The kinematic, trunk endurance and strength measures were analyzed with 2-by-2 analysis of variance
  • Statistical analysis was performed with SPSS Version 21 statistical software (SPSS Inc, Chicago, IL)
  • Significance was set to p < 0.05
Outcome Measures
  • LEFS and VAS scores
  • Trunk muscle endurance and eccentric strength
  • Single-leg squat kinematic and single-leg triple hop for distance results
  • Both groups reported significant reductions in pain at intervention completion and the 3-month post-intervention follow-up (p < 0.001).
  • The FST group noted significantly less pain at the 3-month follow-up compared to the ST group (p = 0.04)
  • Both groups demonstrated significant improvements in LEFS at intervention completion and 3-month post-intervention follow-up (p <0.001)
  • The FST group demonstrated significant improvements in SLTH testing (p < 0.001)
    • The FST group demonstrated significantly greater hop distances at intervention completion compared to the ST group (p = 0.04)

  • At intervention completion, only the FST group noted the following kinematic improvements:
    • ipsilateral trunk inclination (p = 0.004), contralateral pelvic depression (p = 0.005), hip abduction (p = 0.004), knee abduction (p < 0.001), pelvic anteversion (p = 0.01) and hip flexion (p < 0.001) in single-leg squat testing.
    • greater trunk endurance (p < 0.001)
    • greater eccentric strength of the hip abductors (p = 0.001) and knee flexors (p = 0.004)

  • Both groups demonstrated improvements in hip adductor (p = 0.04), hip lateral rotator (p = 0.003) and knee extensor strength (p < 0.001)
Our ConclusionsThe findings demonstrated a reduction in pain and improvements in function in both groups, with the functional stabilization training group (FST) noting larger improvements than the standard training group (ST). These findings suggest that the use of hip strengthening and verbal feedback is superior to quadriceps strengthening for women with PFPS.
Researchers' Conclusions

Hip and knee strengthening along with verbal feedback on proper pelvic and trunk control was more beneficial than quadricep strengthening in females with PFPS.

Review & Commentary: This study adds to the growing body of research supporting the use of hip strengthening exercises for individuals presenting with patellofemoral pain syndrome (PFPS) (10-12). The researchers compared the short-term outcomes of two groups, a functional stabilization (FST) and standardized training group (ST). The FST group underwent hip , hamstring and quadricep strengthening while receiving feedback on appropriate exercise technique. The ST group participated in quadricep strengthening and lower-extremity stretching but did not receive verbal feedback. When compared to the ST group, the FST group made significant improvements in perceived function; single-leg triple hop for distance; self-reported pain; trunk muscle endurance; lower-extremity strength; and kinematic variables during the single-leg squat .

This study had many methodological strengths, including:

  • Group participation was randomly assigned, and participants were unaware of whether they were part of the control or experimental groups.
  • Trunk endurance was measured with exercises commonly used by human movement professionals increasing applicability, including front and side planks and prone extensions .
  • Kinematic variables were measured using the single-leg squat  assessment, which is also commonly used by human movement professionals.
  • The research study compared the methodologies implied by newer research to more conventional methods to aid in optimizing intervention selection.

Weakness that should be noted prior to clinical integration:

  • All participants were recreationally active females which may limit generalizability, to sedentary and/or male populations.
  • Glutues medius strength testing was not included in this study, despite prior research highlighting the relationship between gluteus medius strength and PFPS (3-7).
  • Further research may consider comparing FST and ST groups to a combined FST/ST group, and further to a group not receiving exercise treatment (e.g. patella taping).

How This Study is Important:

Previous research on patellofemoral pain syndrome (PFPS) has demonstrated the effectiveness of hip strengthening (10-12). However, to our knowledge, previous research has not investigated the use of verbal feedback, pre- and post-intervention trunk muscle endurance, and/or compared conventional quadriceps strengthening to a hip strengthening programs. The findings of this study suggest that the hip strengthening and verbal feedback are superior to quadriceps strengthening for resolving symptoms and increasing function of those with PFPS.

How the Findings Apply to Practice:

The findings of this study support the use of hip strengthening, trunk exercises and verbal feedback on lower extremity alignment for clients presenting with patellofemoral pain syndrome (PFPS). Although it cannot be determined from this study whether the addition of quadriceps strengthening would provide additional benefit, if a choice must be made between hip strengthening or quadriceps  research supports the use of hip strengthening.

How This Study Relates to Brookbush Institute Content:

The Brookbush Institute (BI) recommends an integrated approach to addressing any and all dysfunctions/diagnoses, which may include gluteus maximus and gluteus medius  activation for those presenting with patellofemoral pain syndrome (PFPS). Altered trunk muscle recruitment and decreased endurance, altered lower extremity alignment, and inhibition/weakness of the gluteus maximus and gluteus medius  are discussed in the predictive models of Lower-Extremity Dysfunction (LED) , Lumbo Pelvic Hip Complex Dysfunction (LPHCD) , and/or Sacroiliac Joint Dysfunction (SIJD) . This study supports many components of BI's integrated approach to rehabilitation and training, as well as the predictive models of dysfunction that provide a foundation for that approach. Further, this study demonstrates that an integrated approach is superior to conventional models of rehabilitation that attempt to correct a diagnosis with an intervention intended for the painful joint or structure.

Functional Anatomy of the Gluteaus Maximus and Gluteus Medius:

Gluteus Medius Manual Muscle Testing:

Gluteus Medius Activation

Side-Stepping Progressions for Gluteus Medius Strengthening:

Recommended Readings:

  1. Electromyographic Analysis of Hip Rehabilitation Exercises in a Group of Healthy Participants .
  2. Electromyographic Analysis of the Gluteus Medius and Gluteus Maximus During Common Rehabilitation Exercises .
  3. Anterior Hip Capsule Mobilizations Improve Gluteus Maximus Activation.


  1. Boling, M., Padua, D. Marshall, S., Guskiewicz, K., Pyne, S. and Beutler, A. (2010) Gender differences in the incidence and prevelance of patellofemoral pain syndrome. Scandinavian Journal of Medicine and Science in Sports, 20(5), 725-730
  2. Taunton, J. E., Ryan, M. B., Clement, D. B., McKenzie, D. C., Lloyd-Smith, D. R. and Zumbo, B. D. (2002) A retrospective case-control analysis of 2002 running injuries. British Journal of Sports Medicine, 36(2), 95-101
  3. Bolgla, L. A., Malone, T. R., Umberger, B. R. and Uhl, T. L. (2008) Hip strength and hip and knee kinematics during stair descent in females with and without patellofemoral pain syndrome. Journal of Orthopaedic and Sports Physical Therapy, 38(1), 12-18
  4. Bolgla, L. A., Malone, T. R., Umberger, B. R. and Uhl, T. L. (2011) Comparison of hip and knee strength and neuromuscular activity in subjects with and without patellofemoral pain syndrome. International Journal of Sports Physical Therapy, 6(4), 285-296
  5. Ramskov, D., Barton, C., Nielsen, R. O. and Rasmussen, S. (2015) High eccentric hip abduction strength reduces the risk of developing patellofemoral pain syndrome among novice runners initiating a self-structured running program: a 1-year observational study. Journal of Orthopaedic and Sports Physical Therapy, 45(3), 153-161
  6. Boling, M. C., Padua, D. A. and 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
  7. Ireland, M. L., Wilson, J. D., Ballantyne, B. T. and Davis, I. M. (2003) Hip strength in females with and without patellofemoral pain. Journal of Orthopaedic and Sports Physical Therapy, 33, 671-676
  8. Giles, L. S., Webster, K. E., McClelland, J. A. and Cook, J. (2013) Does quadriceps atrophy exist in individuals with patellofemoral pain? A systematic literature review with meta-analysis. Journal of Orthopaedic and Sports Physical Therapy, 43(11), 766-776
  9. Kooiker, L., Van De Port, I. G., Weir, A. and Moen, M. H. (2014) Effects of physical therapist-guided quadriceps-strengthening exercises for the treatment of patellofemoral pain syndrome: a systematic review. Journal of Orthopaedic and Sports Physical Therapy, 44(6), 391-B1
  10. Dolak, K. L., Silkman, C., Medina McKeon, J., Hosey, R. G., Lattermann, C. and Uhl, T. L. (2011) Hip strengthening prior to functional exercises reduced pain sooner than quadriceps strengthening in females with patellofemoral pain syndrome: a randomized clinical trial. Journal of Orthopaedic and Sports Physical Therapy, 41(8), 560-570
  11. Mascal, C. L., Landel, R. and Powers C. (2003) Management of patellofemoral pain targeting hip, pelvis and trunk muscle function: 2 case reports. Journal of Orthopaedic and Sports Physical Therapy, 33(11), 647-660
  12. Nakagawa, T. H., Muniz, T. B., Baldon Rde, M., Dias Maciel, C., de Menezes Reiff, R. B. and Serrao, F. V. (2008) The effect of additional strengthening of hip abductor and lateral rotator muscles in patellofemoral pain syndrome: a randomized controlled pilot study. Clinical Rehabilitation, 22(12), 1051-1060

© 2017 Brent Brookbush

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