title: Clinical Predictors of Knee Mechanics at Return to Sport after ACL Reconstruction.
abstract: OBJECTIVE
  Despite significant rehabilitation, many athletes experience protracted weakness and faulty mechanics after anterior cruciate ligament reconstruction (ACLR). Clinical tests performed early in rehabilitation, which predict knee mechanics at return-to-sport, are virtually unknown and critically needed to guide clinical decision making. The purpose of this study is to determine if quadriceps strength, Y balance anterior (YB-A) reach distance, and single-leg step-down test performance (SLSD) conducted 3 months post-ACLR are predictive of knee flexion excursion (KFLEX) and knee extensor moment (KEM) during running 6 months post-ACLR.
  
  
  METHODS
  Thirty (16 females) subjects were collected 3 and 6 months post-ACLR. Age, 21.3 ± 7.6 yr; mass, 69.85 ± 11.4 kg; height, 1.73 ± 0.09 m. At 3 months post-ACLR, subjects performed isometric quadriceps strength testing, YB-A, and SLSD assessments. At 6 months post-ACLR, subjects underwent three-dimensional motion analysis while running on an instrumented treadmill. Pearson correlation coefficients and stepwise multiple regression were used to assess the relationships of 3-month and 6-month variables.
  
  
  RESULTS
  Quadriceps strength (r = 0.493, P < 0.01), YB-A (r = 0.394, P = 0.03), and SLSD (r = 0.648, P < 0.01) were significantly correlated to KFLEX. Quadriceps strength (0.505, P < 0.01) and SLSD (.541, P < 0.01) were significantly correlated with KEM, whereas YB-A (.276, P = 0.06) was not. SLSD and quadriceps strength were predictive of KEM (adj R², 0.36; P = 0.001) whereas only SLSD was predictive of KFLEX (adj R², 0.40; P < 0.001).
  
  
  CONCLUSIONS
  After ACLR, better performance in SLSD and quadriceps strength 3 months postsurgery is predictive of improved sagittal plane knee mechanics during running 6 months postsurgery.
authors.affiliation: 1Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, Lexington, KY; 2Department of Orthopaedic Surgery and Sports Medicine, University of Kentucky, Lexington, KY; 3Division of Physical Therapy, College of Health Sciences, University of Kentucky, Lexington, KY.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Kline
authors.forename: Darren L
authors.initials: DL
authors.lastname: Johnson
authors.forename: Mary Lloyd
authors.initials: ML
authors.lastname: Ireland
authors.forename: Brian
authors.initials: B
authors.lastname: Noehren
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000534:rehabilitation*; D056352:Athletes; D001696:Biomechanical Phenomena; D005080:Exercise Test; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery*; D008297:Male; D053580:Muscle Strength; D052097:Quadriceps Muscle / Q000502:physiology; D000068958:Return to Sport; D055815:Young Adult