Weak Hip Strength Increases Dynamic Knee Valgus in Single-Leg Tasks of Collegiate Female Athletes

in Journal of Sport Rehabilitation

Clinical Scenario: Dynamic knee valgus (DKV) is a mechanical alteration in the knee that leads to increased risk of injury. Weakness of hip musculature in hip abduction (HABD), extension (HEXT), and external rotation (HER) may contribute to increased DKV in single-leg landing tasks. Focused Clinical Question: Is decreased hip strength associated with an increase in DKV during a single-leg landing task in collegiate female athletes? Summary of Key Findings: Three studies were included: One randomized control trial (RCT), one cohort study, and one case-control. All three studies found that decreases in HABD and HER strength contributed to increased DKV during single-leg landing tasks. One study also found that the hip extensors contribute to controlling hip adduction, a common factor in many mechanisms of injuries. These three studies recommended strengthening HABD, HEXT, and HER to decrease DKV and reduce the risk of injury at the knee. Clinical Bottom Line: Weak HABD, HEXT, and HER contribute to increased DKV in college female athletes, but strengthening HABD, HEXT, and HER can lead to decreases in DKV and, overall, reduce the risk of injury at the knee. Strength of Recommendation: These articles were graded with a level of evidence of III or higher, giving a grade of B strength of recommendation that weak HABD, HEXT, and HER are associated with increased DKV in collegiate female athletes.

Clinical Scenario

Generalized knee pain is one of the most common lower-extremity injuries reported in the clinical setting. It has been reported that women are 3.5 times more likely to suffer from knee injuries when compared with men.1 This increased risk of injury to the knee has often been associated with differences and alterations in their lower-extremity movement patterns. One alteration that has been discussed in the literature and is important to clinicians is dynamic knee valgus (DKV). DKV consists of a combination of increased hip internal rotation and adduction, tibial internal rotation and abduction, and foot pronation.211 These alterations increase abnormal stresses on the tibiofemoral joint and increase the risk of injury, such as anterior cruciate ligament injuries, patellofemoral pain, iliotibial band syndrome, acute lateral ankle sprains, chronic ankle instability, and alterations to balance.211 The improper movement pattern associated with DKV is further emphasized during dynamic movements, especially in single-leg tasks when balance is incorporated into the movement, such as in single-leg landing and single-leg jumping maneuvers.2

The most recent literature on injuries associated with DKV have focused on the clinical utility of hip strengthening.11 DKV is a direct compensation made by individuals with weakness of hip musculature in hip abduction (HABD), hip extension (HEXT), and hip external rotation (HER).24,12 These weaknesses lead to increased valgus at the tibiofemoral joint, and this compensation has been associated with an increased predisposition of injury.5,11 Therefore, the purpose of this critical appraisal topic was to summarize current evidence regarding the effects of how weaknesses in HABD, HEXT, and HER are associated with an increase in the DKV angle during single-leg landing tasks.

Focused Clinical Question (PICO)

Is decreased hip strength associated with an increase in DKV during a single-leg landing task in collegiate female athletes?

Search Strategy

A computerized search was completed in June 2020. The search terms used wereThe criteria for study selection were as follows.

  1. Patient/client group: healthy, college, female athletes
  2. Intervention (or assessment): hip strength, HABD, HEXT, HER
  3. Outcome(s): DKV, knee valgus, single-leg drop jump, single-leg landing task

Inclusion Criteria

  1. Studies that observed kinetic and kinematic variables associated with DKV
  2. Articles with level-III evidence or higher
  3. Limited to the English language
  4. Published in the last 5 years (2015–2020)

Exclusion Criteria

  1. Studies that did not include an athletic female population
  2. Studies that did not show the importance of the hip range of motion strength on the knee

Evidence Quality Assessment

Validity of the studies was determined using the Physiotherapy Evidence Database (PEDro) scale. During the appraisal, each article was reviewed using the PEDro checklist. Within evidence-based medicine, the PEDro scale is a quick clinical tool used to grade the validity of articles to determine their usefulness in clinical decision making. Articles were given a score out of 10 based on criteria related to the study design and quality. The PEDro score for Emamvirdi et al4 was a 9 on the PEDro scale, Malloy et al13 received a 6 on the PEDro scale, and Suzuki et al11 received a 7, losing points for blinding and allocation. These articles were selected because they were graded with a level of evidence of III or higher; studied the effects of HABD, HEXT, and HER; and had DKV as a similar outcome measure. Despite losing points on the PEDro scale, these articles still had relatively consistent results when compared with each other.

Search Results

The summary of the search results and articles can be seen in Figure 1 and Table 1.

Figure 1
Figure 1

Summary of search history and included studies.

Citation: Journal of Sport Rehabilitation 2021; 10.1123/jsr.2021-0043

Table 1

Characteristics of Included Studies

AuthorsEmamvirdi et al4Malloy et al13Suzuki et al11
Study titleThe effect of valgus control instruction exercises on pain, strength, and functionality in active females with patellofemoral pain syndrome.Hip external rotator strength is associated with better dynamic control of the LE during landing tasks.The influence of hip strength on knee kinematics during a single-legged medial drop landing among competitive collegiate basketball players.
Study designRCTCohort studyCase-control study
Participants64 college female volleyball players (age: 22.6 [6.16]) with equal years of exercise experience were eligible to participate in this study. Participants were excluded if they had previous knee injury, instability, effusion, hip pain, or LE surgery.23 female NCAA division I soccer players (age: 19.4 [0.8]) were recruited. Participants were included if they were healthy and had no history of musculoskeletal, neurologic, or cardiovascular injuries or conditions that would limit full participation. Participants were excluded if they had a hip, knee, or ankle injury during the previous season.23 female intercollegiate basketball players (age: 19.96 [0.77]) were eligible to participate in this study. All females were right-limb dominant. Participants were excluded if they had a history of spinal or LE surgery, spinal or LE injury in the past 3 mo, or neurological disorders affecting the LE.
Outcome measuresMaximal HABD and HER strength were collected using a dynamometer. The participants performed 3 successful trials of a single-leg hop test. Data were collected on the knee kinematics using reflective markers.Maximal isometric HABD and HER strength were collected using a handheld dynamometer. The participants performed 3–5 successful trials of a single-leg hop. Data were collected on peak hip and knee kinetics and kinematics using reflective markers and force plates.Maximal isometric HEXT, HABD, prone HER, and seated HER strength were collected using a handheld dynamometer. The participants performed 3 successful trials of a single-leg hop. Data were collected on knee kinematics using reflective markers and force plates.
ResultsThe participants with greater HABD and HER strength demonstrated a statistically significant decrease in DKV. In addition, the participants with greater HABD and HER were able to perform greater single-leg hop tests due to increased strength and control from the HABD and HER muscles. The decrease in DKV during functional single-leg landing tasks is largely a result of HABD and HER strength. Clinicians should consider the role of strengthening HABD and HER to limit DKV.There was a significant relationship between increased HER and decreased peak DKV moment. There was no significant correlation between HABD and decreased DKV. Females with great HER strength have greater control over the femur and knee to decrease DKV during single-leg landing and cutting tasks, leading to a decreased risk of ACL injury. Clinicians should consider strengthening HER in sports requiring single-leg landing and cutting tasks.The participants with greater HEXT, HABD, and prone HER demonstrated decreased DKV during the single-leg hop. The participants had significantly weaker HABD, seated HER, and prone HER isometric strength. They also exhibited significantly greater knee flexion and IR. HABD, HEXT, and HER strength play a significant role in controlling DKV, therefore decreasing the risk of injuries associated with DKV.
Level of evidence1b2b3
Evidence quality score: PEDro967
Support for the answerYesYesYes

Abbreviations: DKV, dynamic knee valgus; HABD, hip musculature in hip abduction; HER, hip musculature in external rotation; HEXT, hip musculature in hip extension; LE, lower-extremity, NCAA, National Collegiate Athletic Association; PEDro, Physiotherapy Evidence Database scale; RCT, randomized controlled trial.

Clinical Bottom Line

Based on the three articles included in this critical appraisal topic and the level of evidence, there is moderate evidence to suggest that weak HABD, HEXT, and HER are associated with increased DKV in collegiate female athletes.2,46,11,13,14 One of the limitations of this critically appraised topic (CAT) is that it included only one RCT; therefore, the suggestions should be taken with some caution.

All three studies included in this CAT reported a deficit in HABD, HEXT, or HER in collegiate female athletes with DKV while performing a single-leg landing task.11,13,14 In addition, the evidence also suggested that increasing HABD, HEXT, and HER will lead to decreases in DKV, which would lead to a reduced risk of injury at the knee.11,13,14

Strength of Recommendation

The studies listed in Table 1 were identified as best evidence and selected for inclusion in this CAT. These articles were selected because they were graded with a level of evidence of III or higher; studied the effects of HABD, HEXT, and HER; and had DKV as a similar outcome measure. Based on the PEDro grading scale, these studies scored a 6/10 or higher and received a grade of B strength of recommendation.

Implications for Practice, Education, and Future Research

The focus of this CAT was to summarize the current literature examining the relationship between hip musculature weakness and DKV angle to determine if those alterations increase the risk of injury at the knee. We learned in this CAT that movements that occur in the knee are controlled by the musculature in the hip, and therefore, alterations to knee kinetics and kinematics are the result of muscular imbalances in the hip.25,12 DKV is an alteration caused by decreases in HABD, HEXT, and HER strength.1,2,6,7,12 When overall neuromuscular control of the hip is decreased or altered, it leads to compensations that force the DKV to increase, which can make the athlete more predisposed to an injury in the entire lower extremity.2,48

The studies included in this CAT addressed the association between weak HABD, HEXT, and HER with increased DKV.11,13,14 It was proven that weak HABD, HEXT, and HER strength leads to increased DKV.11,13,14 Because of this increased abnormal stress at the medial side of the knee, the knee compensates and moves in the path of least resistance to increased valgus. This increase in knee valgus is further emphasized during dynamic movements, especially during a single-leg task.

The results of the three studies included in this CAT suggest that HABD, HEXT, and HER strength should be assessed in athletes to improve DKV and reduce the risk of knee injury.4,1114 Previous research has recorded that the hip extensors primarily control hip adduction (HADD), while hip abductors are more responsible for facilitating hip flexion (HFLEX) and controlling the stability and alignment of the pelvis.14 Considering these findings, clinicians should account for the importance of strengthening HABD and HEXT to reduce the risk of knee injury.14 These results have also been found by other previous research, which had concluded that increased HABD, HEXT, and HER are associated with decreased DKV.11,13 This provides evidence that clinicians should consider strengthening the hip to reduce knee injuries in collegiate female athletes participating in volleyball, basketball, and soccer.1,9,11,1315 Increased hip strength leads to a reduction in injury risk at the knee, including pathologies like anterior cruciate ligament sprains, patellofemoral pain syndrome, and lateral ankle sprains, in addition to any causes for pain.14,6,911,1315 These injuries occur due to malalignments that increase abnormal stressors over time, eventually injuring the structures.

Although there is still conflicting evidence regarding what movements are the greatest contributors to DKV, research does support the evidence that greater hip strength overall is important for decreasing DKV.11,13,14 Because many sports require the athlete to move in fast, dynamic, and multidirectional ways, the opportunity to land in or move from a position of increased DKV is large, and clinicians need to educate coaches and athletes to help strengthen the hip to protect the athlete from risk of injury.9,11 Hip strengthening should not only be used as a rehabilitation technique in athletes who have suffered from an injury, but also in athletes who are more predisposed to sustaining an injury due to the kinematic alterations that put their body at a higher risk of injuries associated with DKV.4,1114

Future research should examine the differences in variables between different tasks, such as a single-leg squat and vertical drop jump, in addition to a single-leg landing, to determine which task(s) most accurately screens athletes for risk of injury and can help screen injured athletes when being cleared to return to competition. In addition, future research is needed to determine whether HABD, HEXT, or HER is the greatest contributor to decreasing DKV. Because the foot and ankle also lead to alterations in the knee, studies need to be done to determine if the hip or the foot and ankle have a greater impact on changes in DKV. Finally, higher quality of evidence, such as randomized control trials and, eventually, systematic reviews and meta-analyses, should be performed to give stronger evidence and additional recommendations regarding this clinical question. This CAT should be reviewed in 2 years to determine whether there is additional best evidence that may change the clinical bottom line for this clinical question.

References

  • 1.

    Rath ME, Stearne DJ, Walker CR, Cox JC. Effect of foot type on knee valgus, ground reaction force, and hip muscle activation in female soccer players. J Sports Med Phys Fitness. 2016;56(5):546553. PubMed ID: 25781215

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2.

    DeJong AF, Colby Mangum L, Resch JE, Saliba SA. Detection of gluteal changes using ultrasound imaging during phases of gait in individuals with medial knee displacement. J Sport Rehabil. 2019;28(5):494504. PubMed ID: 29543116 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Nakagawa TH, Petersen RS. Relationship of hip and ankle range of motion, trunk muscle endurance with knee valgus and dynamic balance in males. Phys Ther Sport. 2018;34:174179. PubMed ID: 30347312 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Emamvirdi M, Letafatkar A, Khaleghi Tazji M. The effect of valgus control instruction exercises on pain, strength, and functionality in active females with patellofemoral pain syndrome. Sports Health. 2019;11(3):223237. PubMed ID: 31034336 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5.

    Hussein AS. The relationship between hip strength and peak knee valgus angle during single leg squat. Nurs Health Sci. 2016;05(04):99106. doi:

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Stickler L, Finley M, Gulgin H. Relationship between hip and core strength and frontal plane alignment during a single leg squat. Phys Ther Sport. 2015;16(1):6671. PubMed ID: 25070759 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7.

    Khamis S, Dar G, Peretz C, Yizhar Z. The Relationship between foot and pelvic alignment while standing. J Hum Kinet. 2015;46(1):8597. doi:

  • 8.

    Wyndow N, de Jong A, Rial K, et al. . The relationship of foot and ankle mobility to the frontal plane projection angle in asymptomatic adults. J Foot Ankle Res. 2016;9(1):3. doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9.

    Barrios JA, Heitkamp CA, Smith BP, Sturgeon MM, Suckow DW, Sutton CR. Three-dimensional hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgum. Clin Biomech. 2016;31:711. PubMed ID: 26515886 doi:

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Rabin A, Portnoy S, Kozol Z. The association of ankle dorsiflexion range of motion with hip and knee kinematics during the lateral step-down test. J Orthop Sports Phys Ther. 2016;46(11):10021009. doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11.

    Suzuki H, Omori G, Uematsu D, Nishino K, Endo N. The influence of hip strength on knee kinematics during a single-legged medial drop landing among competitive collegiate basketball players. Int J Sports Phys Ther. 2015;10(5):592601. PubMed ID: 26491609

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12.

    Burnham JM, Yonz MC, Robertson KE, et al. . Relationship of hip and trunk muscle function with single leg step-down performance: implications for return to play screening and rehabilitation. Phys Ther Sport. 2016;22:6673. PubMed ID: 27592407 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13.

    Malloy PJ, Morgan AM, Meinerz CM, Geiser CF, Kipp K. Hip external rotator strength is associated with better dynamic control of the lower extremity during landing tasks. J Strength Cond Res. 2016;30(1):282291. PubMed ID: 26110347 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14.

    Tate J, Suckut T, Wages J, Lyles H, Perrin B. The associations between hip strength and hip kinematics during a single leg hop in recreational athletes post ACL reconstruction compared to healthy controls. Int J Sports Phys Ther. 2017;12(3):341351. PubMed ID: 28593088

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15.

    Barbosa AC, Vieira ER, Barbosa MA, Fernandes I, Damázio M, Badaró B. Gluteal activation and increased frontal plane projection angle during a step-down test in young women. Hum Mov. 2018;19(1):6470. doi:

    • Crossref
    • Search Google Scholar
    • Export Citation

The authors are with Point Loma Nazarene University, San Diego, CA, USA.

Crowell (kyndellcrowell@outlook.com) is corresponding author.
  • 1.

    Rath ME, Stearne DJ, Walker CR, Cox JC. Effect of foot type on knee valgus, ground reaction force, and hip muscle activation in female soccer players. J Sports Med Phys Fitness. 2016;56(5):546553. PubMed ID: 25781215

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2.

    DeJong AF, Colby Mangum L, Resch JE, Saliba SA. Detection of gluteal changes using ultrasound imaging during phases of gait in individuals with medial knee displacement. J Sport Rehabil. 2019;28(5):494504. PubMed ID: 29543116 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3.

    Nakagawa TH, Petersen RS. Relationship of hip and ankle range of motion, trunk muscle endurance with knee valgus and dynamic balance in males. Phys Ther Sport. 2018;34:174179. PubMed ID: 30347312 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4.

    Emamvirdi M, Letafatkar A, Khaleghi Tazji M. The effect of valgus control instruction exercises on pain, strength, and functionality in active females with patellofemoral pain syndrome. Sports Health. 2019;11(3):223237. PubMed ID: 31034336 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5.

    Hussein AS. The relationship between hip strength and peak knee valgus angle during single leg squat. Nurs Health Sci. 2016;05(04):99106. doi:

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6.

    Stickler L, Finley M, Gulgin H. Relationship between hip and core strength and frontal plane alignment during a single leg squat. Phys Ther Sport. 2015;16(1):6671. PubMed ID: 25070759 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7.

    Khamis S, Dar G, Peretz C, Yizhar Z. The Relationship between foot and pelvic alignment while standing. J Hum Kinet. 2015;46(1):8597. doi:

  • 8.

    Wyndow N, de Jong A, Rial K, et al. . The relationship of foot and ankle mobility to the frontal plane projection angle in asymptomatic adults. J Foot Ankle Res. 2016;9(1):3. doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9.

    Barrios JA, Heitkamp CA, Smith BP, Sturgeon MM, Suckow DW, Sutton CR. Three-dimensional hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgum. Clin Biomech. 2016;31:711. PubMed ID: 26515886 doi:

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10.

    Rabin A, Portnoy S, Kozol Z. The association of ankle dorsiflexion range of motion with hip and knee kinematics during the lateral step-down test. J Orthop Sports Phys Ther. 2016;46(11):10021009. doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11.

    Suzuki H, Omori G, Uematsu D, Nishino K, Endo N. The influence of hip strength on knee kinematics during a single-legged medial drop landing among competitive collegiate basketball players. Int J Sports Phys Ther. 2015;10(5):592601. PubMed ID: 26491609

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12.

    Burnham JM, Yonz MC, Robertson KE, et al. . Relationship of hip and trunk muscle function with single leg step-down performance: implications for return to play screening and rehabilitation. Phys Ther Sport. 2016;22:6673. PubMed ID: 27592407 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13.

    Malloy PJ, Morgan AM, Meinerz CM, Geiser CF, Kipp K. Hip external rotator strength is associated with better dynamic control of the lower extremity during landing tasks. J Strength Cond Res. 2016;30(1):282291. PubMed ID: 26110347 doi:

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14.

    Tate J, Suckut T, Wages J, Lyles H, Perrin B. The associations between hip strength and hip kinematics during a single leg hop in recreational athletes post ACL reconstruction compared to healthy controls. Int J Sports Phys Ther. 2017;12(3):341351. PubMed ID: 28593088

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15.

    Barbosa AC, Vieira ER, Barbosa MA, Fernandes I, Damázio M, Badaró B. Gluteal activation and increased frontal plane projection angle during a step-down test in young women. Hum Mov. 2018;19(1):6470. doi:

    • Crossref
    • Search Google Scholar
    • Export Citation
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