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Tuesday, June 6, 2023

Exercises to Reduce Knee Valgus During Squatting

Brent Brookbush

Brent Brookbush


Research Review: Exercise to Reduce Knee Valgus in Squat

By Jinny McGivern, DPT, Certified Yoga Instructor

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

Original Citation: Bell, D. R., Oates, D. C., Clark, M. A., & Padua, D. A. (2013). Two-and 3-dimensional knee valgus are reduced after an exercise intervention in young adults with demonstrable valgus during squatting. Journal of athletic training,48(4), 442-449. ABSTRACT

Note the blocks under the heels on the right. Indicating much of this dysfunction stems from dorsiflexion restriction. - Source: Bell et. al. 2008 - http://www.somastruct.com/wp-content/uploads/2013/04/kneevalgussquat-600x346.jpg
Caption: Note the blocks under the heels on the right. Indicating much of this dysfunction stems from dorsiflexion restriction. - Source: Bell et. al. 2008 - http://www.somastruct.com/wp-content/uploads/2013/04/kneevalgussquat-600x346.jpg

Note the blocks under the heels on the right. Indicating much of this dysfunction stems from dorsiflexion restriction. - Source: Bell et. al. 2008 - http://www.somastruct.com/wp-content/uploads/2013/04/kneevalgussquat-600x346.jpg

Why is this relevant?:

The double leg squat is a common field test used to identify those with potential lower extremity movement dysfunction and potential predisposition to injury, as medial knee displacement (MKD) has been associated with non-contact ACL injuries. This research provides a specific “prescription” for exercise to reduce MKD during a double leg squat; theoretically reducing one’s risk for non-contact ACL injury. It empowers the human movement professional to use exercise to correct a maladaptive movement pattern

Study Summary

Study Design Randomized Controlled Trial
Level of Evidence 2b - Randomized Control Trial with Small Sample Size
Subject Demographics
  • Age: Intervention group (INT) = 20.9 yrs +/- 2.6; Control group (CON) = 20.4 yrs. +/- 2.9.
  • Gender: INT = 15 female/1 male; CON = 14 female/2 male
  • Characteristics: Healthy & uninjured (no musculoskeletal injury within the previous 6 months). Both groups consisted of individuals with observable medial knee displacement (mid point of patella medial to great toe) occurring in 3/5 squats which was corrected when subjects were provided with 2 in. heel lift.
Outcome Measures
  •  Medial Knee Displacement (MKD) at 0%, 10%, 20%, 30%, 40% & 50% phases of Double Leg Squat (DLS) to 90 degrees via motion analysis
  • 3D Knee Valgus (3DKV) at same percentages as above during DLS via motion analysis
  • Hip strength (Gluteus Maximus, Gluteus Medius, Biceps FemorisSemitedinosus and Semimembranosus) via handheld dynamometry and normalized to body weight
  • Ankle Dorsiflexion Passive Range of Motion (PROM) - Knee straight & Knee bent via standard goniometry
  • Height, mass & age were not significantly different between INT & CON groups.
  • 3DKV was significantly different between groups at pre-test (CON group with less valgus than INT group). MKD was not significantly different between.
  • INT group reduced 3D knee valgus angle from 30-50% of the squat phase.
  • INT group reduced MKD during 20-50% of squat phase.
  • INT group increased ankle dorsiflexion ROM  with knee extended (gastrocnemius flexibility)
  • No significant changes were observed in any of the strength tests for any muscles of the hips tested although strength did demonstrate an increasing trend.
  • No significant change observed in ankle dorsiflexion ROM with knee flexed.
ConclusionsIt appears that ankle dorsiflexion flexibility plays a significant role in mechanics at the knee during the DLS.  Limited sagittal plane motion at the ankle results in a compensation pattern which produces the observed MKD during the DLS. Additional kinematic data is needed to confirm the exact nature of compensation, although it is likely that an increase in subtalar pronation, tibial internal rotation & abduction would produce MKD.
Conclusions of the Researchers A systematic corrective exercise program addressing mobility & strength of both the ankle & hip demonstrated an ability to improve to improve 3DKV & MKD during a DLS.

Review & Commentary:

The overall methodology of this study was quite strong. The researchers took care to standardize the performance of the DLS task with a tripod to mark a depth of 90 degrees of knee flexion, in addition to using markers for foot position to ensure that there were no changes with multiple repetitions. The selection of subjects was highly specific, and focused on those with MKD related to ankle dysfunction (as determined by correction of MKD with heel lift). The 32 subjects that ultimately completed the study were selected from a pool of 85 individuals. Specificity was important because MKD can be the result of dysfunction at the ankle, hip or both, therefore a lack of specificity may have confounded results. The intervention that was carried out had a strong conceptual basis. It utilized the training model of the National Academy of Sports Medicine which consisted of exercises to release & stretch short overactive muscles (in this case gastrocnemius, biceps femoris & hip adductors ), then strengthen & integrate long underactive muscles (medial gastrocnemius , medial hamstring , tibialis posterior). Subjects participated in (10) 30-minute sessions over a 3- week period. This indicates that the intervention has the power to be effective without a tremendous commitment of time from the individual. Progression of exercise was achieved by increasing resistance, sets & reps which allowed the researchers to minimize other potential confounding variables that may have developed with a greater diversity of exercise activities over the course of the 3 weeks.

This research does have limitations. The researcher who performed strength & ROM measurements was not blinded to the subject’s group assignment. An independent rater would have decreased the chance of bias in pre/post intervention measurements. There was no long-term follow-up with the subjects to determine if they retained a reduction in MKD over time. It would have been helpful if the authors included a more detailed description of the exercises in the intervention so that human movement professionals could accurately implement this program. Additionally it would have been interesting to include strength tests of ankle musculature & range of motion measurements for the hip joint in pre-post test measures to see how these parameters changes or didn't change as DLS performance improved.

The researchers discuss that there was a substantial difference in 3DKV between INT & CON groups at baseline, posing a small threat to internal validity. MKD was not significantly different between groups. The authors further explain that previous research found analysis of 3D & 2D data relating to knee valgus do not necessarily correlate. This is an interesting observation which encourages additional avenues of exploration to analyze the difference between these 2 methods of analysis of knee motion. Does one or the other implicate ankle versus hip sources of movement dysfunction?

The authors commented that they did not see significant increases in hip strength at post-test. It is possible that this was due to specificity of subject selection to focus on ankle dysfunction, therefore hip weakness was not present or manifested. It is important to note that specific strengthening activities for the gluteus maximus and gluteus medius were not included as part of the intervention, although they would have been involved in the integrated balance exercises. Other researchers have not found consistent results with respect to the role of hip strength in MKD & knee valgus. An interesting study performed by Mauntel et a l. in 2013 and reviewed on this website found that changes in co-activation ratios, i.e. the amount of activity in the gluteus medius with respect to the adductor group, were demonstrated to be significantly different between those with and without MKD. It is possible that it is not so much the isolated strength of a muscle group that determines the outcome of a movement pattern, but rather how agonists, antagonists, synergists & stabilizers work in collaboration to complete a task.

Future research should look at the relationship between performance on various functional tests such as double leg squat, drop jump and lateral step down, and how different kinematic variables play into each and which are common between them. In order to allow these results to be generalized to other populations, future studies should examine the outcomes of this intervention when carried out for those with knee pathology or injury. Finally a longitudinal study would provide information about whether or not this program is preventative of knee injuries over a sport season or period of time.

Why is this study important?

This study is important because it provides information about the outcomes of implementing an intervention based on a theory of improving human movement. It reinforces the principle that observed dysfunction at 1 joint is often the result of dysfunction at multiple joint segments. Finally, it demonstrates the efficacy of a program that balances improving mobility with improving strength in improving overall movement patterns.

How does it affect practice?

This study provides information on a specific intervention for a specific sub set of individuals. Movement professionals can use this program with clients who have characteristics that match those of the subjects in this study. Additionally, the movement professional can use his/her professional judgement to adapt the information found in this study to apply to clients with some differing characteristics than study participants, but similar presentation of movement dysfunction.

How does it relate to Brookbush Institute Content?

MKD is one of the signs discussed in the Overhead Squat Assessment  ("knees bow in" ) and can be indicative of Lower Leg Dysfunction (LLD)  or Lumbopelvic Hip Complex Dysfunction (LPHCD). This research provides support of the intervention strategy described by the Brookbush Institute to address Lower Leg Dysfuction . Videos below provide descriptions of specific exercises similar to the ones included in this study and this article includes a sample routine . This research supports the use of these types of corrective exercises to reduce MKD during DLS, thus optimizing this movement pattern.

Single Leg Squat performed correctly and incorrectly.
Caption: Single Leg Squat performed correctly and incorrectly.

Single Leg Squat performed correctly and incorrectly. -http://drcaley.com/blog/2014/5/21/the-single-leg-squat-test

Calf Release:

Anterior Adductor Release:

Biceps Femoris Release:

Slant Board Calf Static Stretch:

Adductor Static Stretch:

Biceps Femoris Active Stretch:

Gluteus Medius Activation Progression:

Tibial Internal Rotator Activation:

Posterior Tibialis Activation:

© 2014 Brent Brookbush