title: Squatting mechanics in people with and without anterior cruciate ligament reconstruction: the influence of graft type.
abstract: BACKGROUND
  Single-legged squat mechanics change after anterior cruciate ligament (ACL) reconstruction and rehabilitation, but it is unclear if changes in squat mechanics are graft specific.
  
  
  OBJECTIVE
  To investigate graft differences in biomechanics of the knee, hip, and trunk during the single-legged squat in patients with ACL-reconstructed knees, determine if these factors were associated with deficits in knee extension moment, and determine if subjective knee function and squat biomechanics are related.
  
  
  METHODS
  Cross-sectional study; Level of evidence, 3.
  
  
  METHODS
  A total of 106 individuals were grouped based on surgical status and graft type (51 control, 34 bone-patellar tendon-bone [BPTB], 21 ipsilateral semitendinosus and gracilis autograft [ISGA]). Motion capture interfaced with force plates was used to capture single-legged squat performance in the ACL reconstructed and dominant control limbs. Variables were captured at peak knee flexion.
  
  
  RESULTS
  Controls exhibited greater knee extension moment (P = .04), knee flexion (P = .002), and hip adduction angles (P = .04) compared with the reconstructed groups. The ISGA group demonstrated greater forward (P = .01) and lateral (P = .002) trunk flexion over the reconstructed limb. Summated extension moment did not differ between groups (P = .42). Knee extension moment was correlated with lateral trunk flexion (r = -0.31, P = .03) in the control group and knee flexion angle (r = -0.44, P = .04) in the ISGA group. Subjective knee function scores were correlated with lateral trunk flexion (r = -0.45, P = .008) in the BPTB group and with hip adduction angle (r = -0.46, P = .04) and hip extension moment (r = 0.48, P = .03) in the ISGA group.
  
  
  CONCLUSIONS
  Knee and hip biomechanics were related to surgical status but not graft type. Increased forward and lateral trunk motion in the ISGA group may be a mechanism to protect the knee by minimizing motion during squatting or related to surgical selection bias. Secondary findings (summated extensor moments and correlations) most likely represent a strategy to shift the squat demands from the knee to the hip.
  
  
  CONCLUSIONS
  Clinicians should target these neuromuscular deficits during rehabilitation and training programs after ACL reconstruction.
authors.affiliation: Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin Wisconsin Injury in Sport Laboratory, University of Wisconsin-Madison, Wisconsin Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Wisconsin drbell2@wisc.edu.
authors.forename: David R
authors.initials: DR
authors.lastname: Bell
authors.affiliation: Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin Wisconsin Injury in Sport Laboratory, University of Wisconsin-Madison, Wisconsin.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Kulow
authors.affiliation: Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin Wisconsin Injury in Sport Laboratory, University of Wisconsin-Madison, Wisconsin.
authors.forename: Mikel R
authors.initials: MR
authors.lastname: Stiffler
authors.affiliation: Department of Kinesiology, University of Wisconsin-Madison, Madison, Wisconsin Wisconsin Injury in Sport Laboratory, University of Wisconsin-Madison, Wisconsin.
authors.forename: Mason D
authors.initials: MD
authors.lastname: Smith
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction; D064592:Autografts; D001696:Biomechanical Phenomena / Q000502:physiology; D064594:Bone-Patellar Tendon-Bone Grafts; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D013710:Tendons / Q000637:transplantation
keywords: IKDC; knee extension moment; knee function; summated moment; trunk flexion