title: Abnormal Joint Moment Distributions and Functional Performance During Sit-to-Stand in Femoroacetabular Impingement Patients.
abstract: BACKGROUND
  Femoroacetabular impingement (FAI) is a morphological abnormality of the hip joint that causes pain when performing a mechanically demanding activity of daily living such as the sit-to-stand (STS) task. Previous studies have assessed lower extremity joint mechanics during an STS task in various pathologies, yet the STS task has not been studied in FAI patients.
  
  
  OBJECTIVE
  The objective of this study was to identify differences in joint kinetics and performance between FAI patients and healthy controls during a STS task. It was hypothesized that FAI patients would exhibit altered time needed to complete the STS task, as well as altered lower extremity biomechanics, when compared to healthy controls.
  
  
  METHODS
  This was a cross-sectional cohort study.
  
  
  METHODS
  The study took place at a motion capture laboratory at an institutional orthopedic facility.
  
  
  METHODS
  Biomechanical analysis was performed in 17 FAI patients and 31 age- and body mass index (BMI)-matched healthy controls during the STS task.
  
  
  METHODS
  Sagittal plane joint moments, total support moment (TSM), joint contributions to the TSM, and functional measures during the STS task were compared between groups.
  
  
  METHODS
  Peak joint moments, TSM and joint contributions to the TSM were assessed during the STS task. In addition, the time to and value of the peak vertical ground reaction force (vGRF), limb symmetry index at peak vGRF, loading rate, and total time needed to perform the STS task were determined.
  
  
  RESULTS
  Compared to the control participants, the FAI patients exhibited worse Hip Disability and Osteoarthritis Outcome Score (HOOS) pain and function subscores. No group differences were observed in peak sagittal joint moments during the STS task. However, when compared to controls, the FAI patients demonstrated reduced knee joint contributions to the TSM. In addition, the FAI patients exhibited increased time needed to perform the STS task, increased time to reach peak vGRF, and reduced lower extremity loading rate during the STS task.
  
  
  CONCLUSIONS
  FAI patients demonstrated abnormal joint contributions to TSM and altered functional performance during the STS task. These altered movement patterns during the STS task may be compensatory mechanisms used by the FAI patients to reduce pain and to improve function.
  
  
  METHODS
  Not applicable.
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California-San Francisco, 185 Berry Street, Lobby 6, Suite 350, San Francisco, CA 94107(∗). Electronic address: michael.samaan@ucsf.edu.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Samaan
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California-San Francisco, San Francisco, CA(†).
authors.forename: Benedikt J
authors.initials: BJ
authors.lastname: Schwaiger
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California-San Francisco, San Francisco, CA(‡).
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Gallo
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California-San Francisco, San Francisco, CA(§).
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Link
authors.affiliation: Department of Orthopaedic Surgery, University of California-San Francisco School of Medicine, San Francisco, CA(‖).
authors.forename: Alan L
authors.initials: AL
authors.lastname: Zhang
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California-San Francisco, San Francisco, CA(¶).
authors.forename: Sharmila
authors.initials: S
authors.lastname: Majumdar
authors.affiliation: Musculoskeletal Quantitative Imaging Research Group, Department of Radiology and Biomedical Imaging, University of California-San Francisco, San Francisco, CA; Department of Physical Therapy and Rehabilitation Science, University of California-San Francisco, San Francisco, CA(#).
authors.forename: Richard B
authors.initials: RB
authors.lastname: Souza
mesh_terms: D001696:Biomechanical Phenomena; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D057925:Femoracetabular Impingement / Q000503:physiopathology*; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011187:Posture; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D012720:Severity of Illness Index; D013647:Task Performance and Analysis