title: One-leg hop kinematics 20 years following anterior cruciate ligament rupture: Data revisited using functional data analysis.
abstract: BACKGROUND
  Despite interventions, anterior cruciate ligament ruptures can cause long-term deficits. To assist in identifying and treating deficiencies, 3D-motion analysis is used for objectivizing data. Conventional statistics are commonly employed to analyze kinematics, reducing continuous data series to discrete variables. Conversely, functional data analysis considers the entire data series.
  
  
  METHODS
  Here, we employ functional data analysis to examine and compare the entire time-domain of knee-kinematic curves from one-leg hops between and within three groups. All subjects (n=95) were part of a long-term follow-up study involving anterior cruciate ligament ruptures treated ~20 years ago conservatively with physiotherapy only or with reconstructive surgery and physiotherapy, and matched knee-healthy controls.
  
  
  RESULTS
  Between-group differences (injured leg, treated groups; non-dominant leg, controls) were identified during the take-off and landing phases, and in the sagittal (flexion/extension) rather than coronal (abduction/adduction) and transverse (internal/external) planes. Overall, surgical and control groups demonstrated comparable knee-kinematic curves. However, compared to controls, the physiotherapy-only group exhibited less flexion during the take-off (0-55% of the normalized phase) and landing (44-73%) phase. Between-leg differences were absent in controls and the surgically treated group, but observed during the flight (4-22%, injured leg>flexion) and the landing (57-85%, injured leg<internal rotation) phases in the physiotherapy-only group.
  
  
  CONCLUSIONS
  Functional data analysis identified specific functional knee-joint deviations from controls persisting 20 years post anterior cruciate ligament rupture, especially when treated conservatively. This approach is suggested as a means for comprehensively analyzing complex movements, adding to previous analyses.
authors.affiliation: National Sports Institute of Malaysia, National Sports Complex, Bukit Jalil, Peti Surat 7102, 57700 Kuala Lumpur, Malaysia. Electronic address: hl.kim@isn.gov.my.
authors.forename: Kim
authors.initials: K
authors.lastname: Hébert-Losier
authors.affiliation: MOX - Department of Mathematics, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Pini
authors.affiliation: MOX - Department of Mathematics, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milan, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Vantini
authors.affiliation: Department of Mathematics and Mathematical Statistics, Umeå University, 901 87, Umeå, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Strandberg
authors.affiliation: Department of Mathematics and Mathematical Statistics, Umeå University, 901 87, Umeå, Sweden.
authors.forename: Konrad
authors.initials: K
authors.lastname: Abramowicz
authors.affiliation: Department of Community Medicine and Rehabilitation; Physiotherapy, Umeå University, 901 87, Umeå, Sweden.
authors.forename: Lina
authors.initials: L
authors.lastname: Schelin
authors.affiliation: Department of Community Medicine and Rehabilitation; Physiotherapy, Umeå University, 901 87, Umeå, Sweden.
authors.forename: Charlotte K
authors.initials: CK
authors.lastname: Häger
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000534:rehabilitation; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D013180:Sprains and Strains / Q000503:physiopathology*; D013997:Time Factors
keywords: Biomechanics; Curve analysis; Functional outcomes; Interval testing procedure; Lower extremity; Rehabilitation