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Tuesday, June 6, 2023

Correlation between Patellofemoral Pain Syndrome (PFPS) and Hamstring Over-activity

Brent Brookbush

Brent Brookbush


Research Review: Short Hamstring Length Correlates With Intrinsic Patellofemoral Pain Syndrome

By Nicholas Rolnick SPT, MS, CSCS

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

Original Citation: Kwon O, Yun M, and Lee W. (2014). Correlation between intrinsic patellofemoral pain syndrome in young adults and lower extremity biomechanics. J. Phys. Ther. Sci. 26: 961-964. ARTICLE

Knee Pain Referral Pattern
Caption: Knee Pain Referral Pattern

Knee Pain Referral Pattern - http://www.kneepain.com

Why is this relevant?: Patellofemoral Pain Syndrome (PFPS) is one of the most common orthopedic conditions, affecting an estimated 25% of active individuals between 10 and 35 years of age (1). It has been hypothesized that PFPS originates from increased pressure and stress on the patellofemoral joint due to excessive lateral tracking during knee bending, and that this increased stress may lead to early onset osteoarthritis. Correlations have been made between PFPS and decreased eccentric hip strength (2 ), functional valgus (3 ), latent firing of the vastus medialis obliquus (5,6), and excessive eversion (feet flatten) (7). The current study investigated four prominent biomechanical factors that have been linked with PFPS in the literature, to determine which factor had the strongest correlation with the onset of clinical PFPS.

Study Summary

Study Design Cross-sectional Study
Level of Evidence Level 3
Subject DemographicsSixty (60) individuals, ages 18-25 were recruited from the university setting via convenience sampling, and were split into two groups. The two groups for this experiment were the intrinsic PFPS  group (IPFPS, n = 14) and the control group (CG, n = 42). The IPFPS tested positive in at least two of three diagnostic tests for PFPS (The Modified Functional Index Questionnaire (MFIQ), Clarke's Test, and the Eccentric Step-down Test), but were NOT experiencing knee pain, whereas the control group tested did not test positive for more than one test. Four subjects refused to participate in the experimental testing protocol and were not included in the data analysis.
    • Age (± SD):
      • IPFPS: 22.1 ± 3.2 years old
      • CG: 21.9 ± 2.6 years old

    • Gender (Male/Female, %Male/%Female):
      • IPFPS: 5/9, 35.7/64.3
      • CG: 19/23, 45.2/54.8

    • Characteristics:
      • Other Characteristics of the Subjects
        • Height (cm)
          • IPFPS: 167.4 ± 9.9 cm
          • CG: 167.1 ± 8.3 cm

        • Weight (kg)
          • IPFPS: 62.0 ± 15.9 kg
          • CG: 57.64 ± 9.7 kg

      • Clinical Tests Used to Classify Individuals in the IPFPS Group
        • Modified Functional Index Questionnaire - MFIQ
          • The MFIQ is a measurement tool consisting of 10 questions (rated 1-10, higher scores indicate more difficulty/pain) related to pain, dysfunction, and functional tasks (such as climbing a flight of stairs).

        • Clark's Test
          • This is a commonly used provocative test to assist in the clinical diagnosis of PFPS. Individuals with PFPS commonly have pain with this test.
          • Procedure: With the subject in supine the examine compressed the patella. The subject is asked to contract their quadriceps muscle and note any pain with the contraction.

        • Eccentric Stepdown Test
          • Individuals with PFPS commonly complain of pain and/or inability to control the knee while stepping off a step.
          • Procedure: Subjects stood on a 15cm high box and were instructed to "stand straight on the step and very slowly step down." If one leg was performed successfully, the same procedure was repeated for the other leg.

      • After the initial assessments for PFPS (above) were performed, subjects were allocated into the IPFPS or CG.
      • Biomechanical analyses were performed on each of the groups. Each of the biomechanical analyses performed were linked in the literature as a risk factor for development of PFPS.
        • Shortening of the hamstring muscle
          • Hamstring shortness was measured using the straight leg raise test, recording angle of hip flexion.

        • Navicular Drop Test (NDT)
          • The NDT was used to measure the amount of pronation.
          • Procedure: A graduated ruler was used to measure the NDT. The exact experimental protocol was not specified, other than the measurement was taken in weightbearing at the navicular and in non-weightbearing.

        • Q-angle
          • Angle formed by a line drawn from the ASIS to central patella and a second line drawn from central patella to tibial tubercle.
          • Procedure: Subjects stood without shoes on, with their knees locked out (in a comfortable position) looking straight ahead.

        • Dynamic Quadriceps Angle (DQA)
          • It has been proposed that the DQA is larger in those individuals with PFPS.
          • Procedure: A camcorder (SONY DCR-SR 300) was used to measure the DQA. Each subject descended a 15cm stair with one leg bent at the knee and the other straight, looking forward with their feet set shoulders width apart in a comfortable position. During the stair descent, the heel remained on the step. The process was repeated three times, with the average of the three used for data analysis (on Dartfish, a software program that allows joint angles to be measured). The camcorder served as another mode of analysis for each of the subjects.

      • Statistical Analyses
        • Independent t-tests and Spearman's correlation analysis were conducted to determine correlations of IPFPS with the biomechanical variables of interest (hamstring shortness, NDT, SQA, and DQA). Significance was set at p < 0.05.

  • Inclusion Criteria: N/A
  • Exclusion Criteria:
    • Subjects were excluded if they had any lower limb pathology, neuropathology, or any history of knee surgery.

Outcome Measures
  • IPFPS Tests (compared between IPFPS and CG)
    • MFIQ Scores (scores of 0,5,10,15,25,35,50)
    • Right/Left Side (+,-) Clark's test
    • Right/Left Side (+,-) Eccentric Stepdown test

  • Biomechanical Risk Factors (compared between IPFPS and CG)
    • Right/Left Hamstring tightness (in degrees, standard deviation)
    • Right/Left Static Q-Angle (in degrees, standard deviation)
    • Right/Left Dynamic Q-Angle (in degrees, standard deviation)
    • Right/Left Navicular Drop Test (in cm, standard deviation)

Results IPFPS Tests
  • MFIQ Scores (not statistically significant between groups in any category)
  • Clark's Test (IPFPS vs. CG, % of total subjects)
    • Right side (+) - 100% vs. 26.2%
    • Right side (-) - 0% vs. 73.8%
    • Left side (+) - 35.7% vs. 21.4%
    • Left side (-) - 64.3% vs. 78.6%

  • Eccentric Stepdown (IPFPS vs. CG, % of total subjects)
    • Right side (+) - 28.6% vs. 0%
    • Right side (-) - 71.4% vs. 100%
    • Left side (+) - 21.4% vs. 0%
    • Left side (-) - 78.6% vs. 100%

Biomechanical Factors

  • Hamstring tightness (°, standard deviation) (IPFPS vs. CG, * indicates p < 0.05)
    • Right - 77.0 ± 5.9 vs. 80.8 ± 6.2*
    • Left - 78.0 ± 7.5 vs. 79.4 ± 7.0

  • Static Q-Angle (°, standard deviation)
    • Right - 19.8 ± 5.8 vs. 18.0 ± 5.4
    • Left - 20.0 ± 6.6 vs. 20.2 ± 6.1

  • Dynamic Q-Angle (°, standard deviation)
    • Right - 18.6 ± 7.7 vs. 19.5 ± 8.5
    • Left - 21.1 ± 9.7 vs. 23.6 ± 9.0

  • Navicular Drop Test (cm, standard deviation)
    • Right - 1.1 ± 0.4 vs. 1.0 ± 0.3
    • Left - 0.9 ± 0.4 vs. 0.9 ± 0.4

ConclusionsRight hamstring tightness was significantly different between the CG and IPFPS group, while all other biomechanical variables investigated showed no differences between groups.
Conclusions of the Researchers There exists a strong correlation between and PFPS and hamstring tightness.

A lecture by Dr. Brent Brookbush for Rowan University, &#34;Introduction to Functional Anatomy&#34;. In this lecture Dr. Brookbush is explaining tibial rotation and the hamstrings.
Caption: A lecture by Dr. Brent Brookbush for Rowan University, &#34;Introduction to Functional Anatomy&#34;. In this lecture Dr. Brookbush is explaining tibial rotation and the hamstrings.

A lecture by Dr. Brent Brookbush for Rowan University, "Introduction to Functional Anatomy"

Review & Commentary:

The current study exhibits several strengths in its methodology. The study used clear inclusion and exclusion criteria, as well as, easy to replicate protocols. The authors did use common clinical tests for the diagnosis of PFPS, although the specificity and sensitivity of those tests (especially Clark's Sign) may be a little low. The highlight of this study is the intention of the author's. The authors' goal was to determine the most relevant factors associated with PFPS, by comparing risk factors that had been previously correlated with PFPS in the literature. In doing so, the authors identified hamstring tightness as the variable most highly correlated with PFPS. Although this is not a systematic review, this does add strength to the study, as this study compared evidence-based factors rather than hypothesized factors. An interesting side note of this study: 25% of the university students recruited tested positive in 2 or more clinical tests associated with the diagnosis of PFPS.

The current investigation also had some weaknesses that should be mentioned before the results are integrated into practice. First, while the methods were adequately described, some portions of the assessment protocols were unclear. One example was the lack of description of how the hamstring length test (straight leg raise test) was measured. No mention was made regarding whether goniometry was used to determine the angle, and whether the "resistance barrier" used for end range was active, passive, active with over-pressure, etc. Second, a power analysis was not performed prior to the intervention, so it is unknown what numbers would have been needed to achieve statistical significance in the other variables investigated in the current study - this includes the navicular drop test, which trended towards statistical significance. Although the tests used for the inclusion criteria were commonly used clinical tests, a review of the tests reliability may have swayed the authors's away from the "Clark's sign test" which has notoriously low specificity. Last, the intervention was performed on asymptomatic healthy individuals. Therefore, results of this current study should not be ascribed to individuals with clinically diagnosed PFPS. Future studies should compare IPFPS with clinical PFPS to determine if the trend of hamstring tightness continues in this population.

Why is this study important?

The current study grouped individuals into those who tested positive for 2 or more tests (IPFPS group) and those that tested positive for 1 or less tests (the CG), and then compared 4 different biomechanical factors that have been correlated with the presence of PFPS. Of the 4 factors investigated, the researchers concluded that the IPFPS group had significantly shorter hamstring length on the affected side than the CG. This implies that of these 4 factors, hamstring length has the highest correlation with knee pain. Further, the navicular drop test trended towards statistical significance. Increased pronation has previously been linked to increased medial knee displacement, a factor associated with knee pain (4). More research is needed with larger sample sizes comparing additional factors that have been proposed to contribute to the onset of PFPS.

How does it affect practice?

The current study suggests that hamstring length may have the highest correlation to PFPS of the 4 factors measured (navicular drop, Q-angle, dynamic Q-angle and straight leg raise). The assessment used in this study, the straight leg raise, could be used to determine relative tightness of the hamstring complex. The individuals in the study tested positive to clinical tests, but were asymptomatic, suggesting this test may also be used as a screen to address biomechanical issues before symptoms affect activities of daily living. Individuals should be able to achieve 80-90° of hip flexion with the leg straight and minimal pelvic motion.

How does it relate to Brookbush Institute Content?

Patellofemoral pain syndrome (PFPS) is a common diagnosis, however this diagnosis may be a symptom of postural dysfunction/movement impairment. PFPS is indicated as a possible issue in the predictive models of postural dsyfunction - lumbo-pelvic hip complex dysfunction (LPHCD) , sacroiliac joint dysfunction (SIJD) and lower leg dysfunction (LLD) . In all of these models, the biceps femoris is over-active. Specifically, the long head of biceps femoris commonly adopts a maladaptive increase in length and activity, while the short head becomes adopts a maladaptive decrease in length and increase in activity. This may imply that both heads would benefit from release techniques , while the short head may require additional lengthening techniques . The medial hamstring musculature (semitendinosus/semimembranosus ) tends to adopt a maladaptive decrease in activity and increase in length, and may require activation and integration techniques . The current study suggests that hamstring tightness correlates to onset of clinical PFPS, but based on all evidence, additional benefit may be attained by a more detailed approach to hamstring extensibility and activity.

The Brookbush Institute approaches postural dysfunction by releasing over-active musculature (biceps femoris - long/short head ), mobilizing stiff joints (knee ) and activating and integrating under-active musculature (semimembranosus/semitendinosus ).

The following videos are steps in assessing and addressing inadequate hamstring length in practice.

Brookbush Institute Videos

Hamstrings Review

Goniometric Assessment of Hamstring Length

Biceps Femoris Static Release

Biceps Femoris Dynamic Release

Biceps Femoris Active Stretch

Tibial Internal Rotator Activation


  1. Muller K, Snyder-Mackler L. (2000). Diagnosis of patellofemoral pain after arthroscopic menisectomy. JOSPT. 30: 138-142.
  2. Ramskov, D., Barton, C., Nielsen, R. O., & Rasmussen, S. (2015). High Eccentric Hip Abduction Strength Reduces the Risk of Developing Patellofemoral Pain Among Novice Runners Initiating a Self-Structured Running Program: A 1-Year Observational Study. journal of orthopaedic & sports physical therapy45(3), 153-161.
  3. Dos Reis, A. C., Correa, J. C. F., Bley, A. S., Rabelo, N. D. D. A., Fukuda, T. Y., & Lucareli, P. R. G. (2015). Kinematic and Kinetic Analysis of the Single-Leg Triple Hop Test in Women With and Without Patellofemoral Pain. journal of orthopaedic & sports physical therapy, 45(10), 799-807.
  4. Steinberg N, Firestone A, Noff M, et al. (2013). Relationship between lower extremity alignment and hallux valgus in women. Foot Ankle Int. 34(6): 824-831. doi: 10.1177/1071100713478407.
  5. Van Tiggelen D, Cowan S, Coorevits P, Duvigneaud N, Witvrouw E. Delayed Vastus Medialis Obliquus to Vastus Lateralis Onset Timing Contributes to the Development of Patellofemoral Pain in Previously Healthy Men. Am J Sports Med June 2009
  6. Tang, Simon F.T. et al., Vastus medialis obliquus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patellofemoral pain syndrome: An electromyographic study Archives of Physical Medicine and Rehabilitation , Volume 82 , Issue 10 , 1441 – 1445
  7. Smith, J. A., Popovich, J. M., & Kulig, K. (2014). The influence of hip strength on lower limb, pelvis, and trunk kinematics and coordination patterns during walking and hopping in healthy women. Journal of Orthopaedic & Sports Physical Therapy, (Early Access), 1-23.

© 2016 Brent Brookbush

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