Influence of frontal plane knee angle and hip strength on medial knee joint loading during walking gait in individuals with anterior cruciate ligament reconstruction

  • Luc B
  • Blackburn J
  • Stanley L
  • et al.
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Purpose: Patients with a history of knee injury have over 400% higher odds of developing knee osteoarthritis (OA). Approximately one-third of anterior cruciate ligament (ACL) injured patients that undergo surgical ACL reconstruction (ACLr) rapidly develop OA within 10 years of injury. One critical goal of post-ACLr rehabilitation is to regain lower extremity muscle strength and functional movement biomechanics to decrease disability and maintain long-term knee joint health. Greater knee varus angles during gait have been linked to greater external knee adduction moments (KAM) during gait in patients with knee OA. Excessive KAM increases medial tibiofemoral joint loading, which may increase the rate of OA progression following knee injury. Optimal hip strength may aid in proper positioning of the lower extremity during gait, potentially altering frontal plane motion and reducing KAM. Open kinetic chain hip muscle strength can easily be assessed clinically via hand held dynamometry (HHD), but it is unknown if hip muscle strength influences KAM. The purpose of this study was to determine the associations between hip strength and KAM during gait in ACLr patients. Additionally, if strength was associated with KAM we sought to determine if strength associated with KAM after accounting for variance associated with knee varus kinematics during gait. Methods: Twenty individuals with a history of unilateral ACLr participated (70% Female, 43.8 +/- 29.8 months post ACLr, 21.2 +/- 2.3 years old, 73.3 +/- 19.6kg, 1.7 +/- 0.1m). An optoelectric motion analysis system integrated with force plates was used to acquire kinetic and kinematic gait data as subjects walked along a 6m walkway at a self-selected speed. Kinetic and kinematic data were visually inspected before being filtered and processed with in-house algorithms (LabView v 12.0). Peak KAM was determined using standard inverse dynamics calculations and extracted from the first 50% of stance phase of gait. Frontal plane knee angle, with varus represented as a positive value, was determined at initial heel strike (FrontalHS) of the stance phase of gait. We also determined the peak knee varus angle during the first 50% of stance phase (FrontalPEAK). KAM was normalized to the product of body weight and height. Hip strength using HHD was determined for: 1) hip abduction (ABD), 2) hip internal rotation (IR) and 3) hip external rotation (ER). Participants were positioned prone for measurement of IR and ER or side lying for ABD strength. The peak value of three trials were averaged and normalized to each participant's body weight. Separate Pearson product moment correlations were used to assess simple associations between 1) frontal plane knee angle and KAM and 2) hip strength and KAM. If a simple association existed between a strength variable and KAM, that strength variable was entered into separate hierarchical linear regression models for each kinematic variable. The change in R2 was determined for each regression model to determine if the strength variable explained a significant amount of variance in KAM after separately accounting for kinematic variables (FrontalHS and FrontalPEAK). Alpha level was set a priori at p<0.05. Results: FrontalHS (r=0.691, p=0.001), FrontalPeak (r=0.711, p<0.001) and hip ER strength (r=0.678, p=0.001) were moderately associated with KAM. We found no other significant associations between hip strength and KAM (r=-0.15 to 0.25). After accounting for FrontalHS, hip ER explained 12.6% (DELTAR2 = 0.126, p= .03) of the variance in the regression model predicting KAM (R2 = 0.6, p< .001). Similarly, after accounting for FrontalPeak, hip ER explained 12.2% (DELTAR2 = 0.122, p= .03) of the variance in the regression model predicting KAM (R2 = 0.628, p< .001). Conclusions: In contrast to our hypothesis, higher hip ER strength was associated with higher KAM during gait in the involved limb of ACLr patients, even after accounting for the amount of knee varus (FrontalHS and FrontalPeak) at two points during the stance phase of gait. Open chain hip IR and ABD st




Luc, B. A., Blackburn, J. T., Stanley, L. E., Pamukoff, D. N., Mauntel, T. C., Frank, B. S., … Pietrosimone, B. (2015). Influence of frontal plane knee angle and hip strength on medial knee joint loading during walking gait in individuals with anterior cruciate ligament reconstruction. Osteoarthritis and Cartilage, 23, A115.

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