title: Hop testing provides a reliable and valid outcome measure during rehabilitation after anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  Although various hop tests have been proposed as performance-based outcome measures following anterior cruciate ligament (ACL) reconstruction, limited reports of their measurement properties exist. The purpose of this study was to investigate the reliability and longitudinal validity of data obtained from hop tests during rehabilitation after ACL reconstruction.
  
  
  METHODS
  Forty-two patients, 15 to 45 years of age, who had undergone ACL reconstruction participated in the study.
  
  
  METHODS
  The study design was prospective and observational with repeated measures. The subjects performed a series of 4 hop tests on 3 separate occasions within the 16th week following surgery and on a fourth occasion 6 weeks later. The tests were a single hop for distance, a 6-m timed hop, a triple hop for distance, and crossover hops for distance. Performance on the ACL-reconstructed limb was expressed as a percentage of the performance on the nonoperative limb, termed the "limb symmetry index." Subjects also completed the Lower Extremity Functional Scale and a global rating of change questionnaire.
  
  
  RESULTS
  Intraclass correlation coefficients for limb symmetry index values ranged from .82 to .93. Standard errors of measurement were 3.04% to 5.59%. Minimal detectable changes, at the 90% confidence level, were 7.05% to 12.96%. Changes in hop test scores on the operative limb were statistically greater than changes on the nonoperative limb. Pearson correlations (r) between change in hop performances and self-reported measures ranged from .26 to .58.
  
  
  CONCLUSIONS
  The results show that the described series of hop tests provide a reliable and valid performance-based outcome measure for patients undergoing rehabilitation following ACL reconstruction. These findings support the use and facilitate the interpretation of hop tests for research and clinical practice.
authors.affiliation: John Owen Pavilion, University of British Columbia, Vancouver, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Reid
authors.forename: Trevor B
authors.initials: TB
authors.lastname: Birmingham
authors.forename: Paul W
authors.initials: PW
authors.lastname: Stratford
authors.forename: Greg K
authors.initials: GK
authors.lastname: Alcock
authors.forename: J Robert
authors.initials: JR
authors.lastname: Giffin
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D016118:Anterior Cruciate Ligament / Q000503:physiopathology / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019651:Plastic Surgery Procedures; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D016896:Treatment Outcome