title: Effect of body mass index on knee function outcomes following continuous passive motion in patients with osteoarthritis after total knee replacement: a retrospective study.
abstract: OBJECTIVE
  Obesity may influence postoperative rehabilitation outcomes after total knee replacement (TKR). The aim of this study was to evaluate the effects of body mass index (BMI) on the progression of inpatient rehabilitation using continuous passive motion (CPM) and its treatment outcomes.
  
  
  METHODS
  A retrospective study was conducted in a rehabilitation centre. In total, 354 patients undergoing primary TKR were enrolled through medical chart review.
  
  
  METHODS
  All patients commenced the CPM programme immediately after surgery and continued until hospital discharge.
  
  
  METHODS
  Knee flexion, pain score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) physical function score.
  
  
  METHODS
  Patients were divided into five BMI groups: normal weight (n=59), overweight (n=95), Class I obesity (n=90), Class II obesity (n=82) and Class III obesity (n=28). All outcome measures were recorded at admission; daily during the inpatient stay; at discharge; and at 1-, 3- and 6-month follow-up assessments.
  
  
  RESULTS
  During CPM exercises, obese patients had a smaller initial flexion angle (P<0.001) and a smaller daily increment in the CPM motion arc (P<0.001) compared with patients of normal weight. Severe obesity was associated with poor knee flexion [adjusted odds ratio (aOR) 11.9, 95% confidence interval (CI) 3.49 to 40.94, P<0.001] and WOMAC physical function score (aOR 5.09, 95% CI 1.62 to 16.03, P=0.005) at 6-month follow-up.
  
  
  CONCLUSIONS
  Obesity had a negative effect on progress during the CPM protocol, which commenced immediately after surgery and continued until discharge. Obesity was also associated with poorer self-reported function at 6-month follow-up.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan; School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: C-D
authors.initials: CD
authors.lastname: Liao
authors.affiliation: Department of Exercise and Health Science, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan.
authors.forename: Y-C
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Department of Orthopaedics, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: Y-S
authors.initials: YS
authors.lastname: Chiu
authors.affiliation: Department of Physical Medicine and Rehabilitation, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan; Graduate Institute of Injury Prevention and Control, Taipei Medical University, Taipei, Taiwan; Department of Physical Medicine and Rehabilitation, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan. Electronic address: peter_liou@s.tmu.edu.tw.
authors.forename: T-H
authors.initials: TH
authors.lastname: Liou
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000534:rehabilitation*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D015915:Motion Therapy, Continuous Passive / Q000379:methods*; D009765:Obesity / Q000453:epidemiology*; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000601:surgery; D010146:Pain; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012189:Retrospective Studies; D012737:Sex Factors
keywords: Continuous passive motion; Functional outcome; Obesity; Rehabilitation; Total knee replacement