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Tuesday, June 6, 2023

Lower Extremity Muscle Activation Patterns in Individuals with Knee Valgus

Brent Brookbush

Brent Brookbush


Research Review: Lower Extremity Muscle Activation Patterns in Individuals with Knee Valgus

By Jinny McGivern, DPT, Certified Yoga Instructor

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

Original Citation:

Padua, D. A., Bell, D. R., & Clark, M. A. (2012). Neuromuscular characteristics of individuals displaying excessive medial knee displacement. Journal of athletic training, 47(5), 525. ARTICLE

Why is this relevant?:

Medial knee displacement (or knee valgus) during a double leg squat has been associated with injuries as well as degenerative conditions of the lower extremity. This indicates that we can consider it a maladaptive movement pattern or a movement dysfunction . In order to correct a maladaptive movement pattern it is essential to understand both the characteristics of that motion, i.e. the specific joint actions that make up the dysfunction , as well as the neuromuscular mechanisms that produce those joint actions. This research provides key information about the neuromuscular characteristics of selected muscles of the lower extremity in those demonstrating this movement dysfunction . This information allows the human movement professional to tailor their interventions to target specific muscles & select the most appropriate types of activity to reduce dysfunction.

Study Summary

Study Design Descriptive Laboratory Study
Level of Evidence 2b - Individual Cohort Study
Subject Demographics
  • Age: Medial Knee Displacement (MKD) group = 20.2 yrs +/- 1.9; Control/non-MKD group (CON) = 21.3 yrs +/-2.3
  • Gender: MKD = 15 female/3 male; CON = 15 female/4 male
  • Characteristics: Healthy & uninjured (no musculoskeletal injury within the previous 3 months).  Criteria for inclusion in MKD group included visually observable movement of the mid point of the patella medial to the great toe during double leg squat which corrected when squat was performed with a 2 in. heel lift.  Criteria for CON group was that knees remained over toes during squat in both non-heel lift & heel lift conditions.   Exclusion criteria: Individuals with MKD present during both heel lift & non-heel lift conditions.
Outcome Measures EMG activity of the following muscles:

during both the descending & ascending phases of a double leg squat,

during 2 conditions: No Heel Lift (i.e. feet flat on floor) & Heel Lift (2 in. heel lift).

Quantity of frontal plane medial knee displacement of dominant lower extremity (the one used for kicking) during double leg squat

Results Hip Musculature:
  • No significant differences between groups in GMED & GMAX activity during any phase of squat or either condition.
  • MKD group demonstrated increased ADD activity as compared to controls during both phases of squat, under both conditions.

Lower Leg Musculature:

  • MKD group demonstrated greater TA activation during descending phase of squat in no heel lift & heel lift conditions, as compared to CON group. No significant  differences were noted between groups during the ascending phase. Both groups demonstrated comparable percentages of decreased TA activation during heel lift condition (MKD 55%; CON 52%).
  • Side of muscle (MedG vs. LatG) was not noted to have a main effect during either phase of squat or condition. Data from both of these muscles was pooled for analysis and is represented as (GS).
  • MKD group demonstrated greater GS activity than CON during descending phase of no heel lift condition. During the heel lift condition, MKD group demonstrated decreased GS activity (although it remained higher than CON).  There was no difference in GS activity for CON group between conditions.

Medial Knee Displacement:

  • Was unchanged in CON group between conditions.
  • Decreased in MKD group with heel lift (although did not decrease below values of CON group).
ConclusionsIt appears that individuals demonstrating MKD correctable with a 2 in. heel lift demonstrate altered neuromuscular activation at both the hip & ankle joints.  While the addition of a heel lift resulted in differences in activation at the ankle & decreased MKD, no changes in activation were observed at the hip joint.
Conclusions of the ResearchersDuring a squat, MKD has been observed to be associated with increased neuromuscular activity of the ADD, TA & GS.  The addition of a heel lift resulted in decreased activation of both TA & GS muscles (ADD activity was unchanged), & resulted in a reduction of MKD. It appears that dynamic ankle stiffness has a role to play in increasing MKD although a cause & effect relationship can not yet be determined.  The conceptual model proposed by the authors is that increased GS & TA stiffness limiting ankle dorsiflexion results in increased calcaneal eversion, talar adduction & tibial internal rotation, which is observed as MKD during squat.


Can you visualize how limited motion in the sagittal plane at the ankle (dorsiflexion) might lead to a "borrowing of motion" from the transverse plane (tibial & talar rotation) during a squat?

Review & Commentary:

This was a well conducted study which carefully examined neuromuscular activation patterns of the lower extremity during the double leg squat task. Although the study did have a small sample size, the researchers were very specific in their subject selection (only those where MKD was corrected with a heel lift). Furthermore, they were also very specific in standardization of the performance of this task (controlled depth of squat with a tripod & speed of squat with a metronome).

The major limitation of this study, which the authors acknowledge, was that hip & ankle kinematics (i.e. movement characteristics) were not quantified. Although we can hypothesize that the observed increase in activity of the GS & TA during a double leg squat resulted in decreased ankle dorsiflexion , leading to changes in foot mechanics which ultimately resulted in changes in motion of the tibia, which lead to the observed medial knee displacement, this cannot be said for certain because these motions were not measured during this study. Future research should investigate the kinematics of the ankle during the double leg squat task. It would be additionally beneficial if future research investigated the role of other muscles of the lower extremity, possibly using needle EMG in order to gain greater accuracy in measurement of muscle activity. Other muscles of interest might be the extensor hallucis longus, extensor digitorum longus , tibialis posterior , the fibularis muscle group , as well as the quadriceps & the hamstrings.

One finding of this research was that ADD activity was increased in the MKD group as compared to controls. It is interesting that although MKD was reduced with the heel lift condition, ADD  activity remained unchanged. It is possible that although ADD  activity is different between those with and without MKD, it may not be the main cause of dysfunction if MKD corrects with a heel lift. This information encourages the human movement professional to take the time to determine if the cause of MKD is primarily related to hip or ankle mechanisms, and to monitor if this changes throughout the course of an intervention.

The most surprising finding of this study (in my opinion) was the increased TA activation in the MKD group. It was not surprising to learn that this group demonstrated increased activation of the GS . It makes sense that a muscle that performs plantar flexion could have the power to limit dorsiflexion . However TA is a muscle that performs dorsiflexion, the very movement that is needed to successfully perform a double leg squat. Is it possible that TA activation increased in response to increased GS activity - an attempt to actively perform the movement to overcome the stiffness caused by increased activity of the GS ? Maybe. Is it possible that the increased activation of TA might have a role to play in changing kinematics at the ankle , possibly contributing to tibial internal rotation when the foot is fixed? Potentially. One thing is for certain: research leads us to ask more questions, which leads to more research, which leads to more questions. This allows us to continuously refine our work as human movement professionals. There is more to learn about the activation patterns of muscles of the lower leg in those with MKD, as there is also more to learn about the effects of specific interventions to alter these activation patterns to correct dysfunction .

Why is this study important?

This study is important because it provides descriptive data about the differences in neuromuscular activation between individuals utilizing a mal-adaptive movement pattern versus those using a more optimal movement pattern. Human movement professionals can use this information as an intellectual springboard to design interventions & programs to assist clients in correcting movement dysfunction. It is important to remember that this particular study does not support or refute the use of a specific intervention program to reduce MKD. It provides information about the neuromuscular qualities of movement in health, young individuals with this dysfunction, which we can use to develop intervention programs which must then be evaluated for their effectiveness.

How does this affect practice?

This research provides the human movement professional with information about some of the muscles involved in creating MKD and also what role they play in this dysfunction , that is, overactive vs. underactive. This informs the type of technique we use to address a given muscle or muscle group when we encounter this movement pattern. Do we want to inhibit the activity of a given muscle through static release techniques & stretching or do we want to increase a muscle's activity through targeted activation & then whole body integration activities?

How does it relate to Brookbush Institute Content?

This research supports the Brookbush Institute's predictive model of postural dysfunction regarding Lower Leg Dysfunction . As mentioned above, it was not surprising to find that the GS is overactive in individuals with MKD. It was also not surprising to find that the ADD  have higher activity levels than in those with MKD than those without. Videos below discuss methods of releasing & stretching the GS as well as the ADD . These are both inhibitory techniques. Based on the findings in this study, one might assume that it would also be wise to release & stretch the TA , as it was found to have higher levels of activity in the MKD. This finding is not consistent with the conceptual model of Lower Leg Dysfunction . TA is typically treated as a muscle that is underactive, therefore a candidate for activation & integration techniques. This research does not allow us to fully grasp why the TA may have been more active in those with MKD as opposed to those without, even with the heel lift condition. In the hyperlinked article on the TA , this study is mentioned with a hypothesis regarding arthrokinematic dysfunction at the talonavicular joint contributing to increased activity. At this time, the Brookbush Institute continues to recommend releasing GS & activating TA in order to allow more optimal ankle dorsiflexion during a squat. However, keep in mind that as new research emerges with information about the activation patterns of other muscles of the lower leg and about successful interventions to reduce MKD, it may be necessary for us to revise our strategy for managing TA .

Gastroc and Soleus (Calf) SA Static Release

Adductor Magnus (Posterior) SA Static Release

Calf and Fibularis Peroneal SA Static Stretching Technique

Static Anterior Adductor Stretch Anterior

Tibialis Anterior Isolated Activation

© 2014 Brent Brookbush

Questions, comments, and criticisms are welcomed and encouraged!