title: Knee flexion contractures in patients with osteoarthritis: clinical features and histologic characterization of the posterior capsule.
abstract: OBJECTIVE
  To (1) identify demographic and clinical factors associated with knee flexion contracture (KFlC) in the setting of osteoarthritis (OA) and (2) histologically compare the posterior knee capsule of patients with OA with and without KFlC.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Primary care, including private and institutional practice.
  
  
  METHODS
  Thirteen patients with primary OA and KFlC and 8 patients with primary OA without KFlC.
  
  
  METHODS
  We compared the KFlC and non-KFlC groups to identify demographic and clinical factors associated with KFlC. We examined the histology of the posterior knee capsules of 9 patients with KFlC and 6 without.
  
  
  METHODS
  Patient demographic and clinical factors. For histology we measured the proportional composition of collagenous, adipose, and synovial tissues; fibroblast and adipocyte cellularity; and synovial thickness.
  
  
  RESULTS
  Patients with contracture had longer duration of OA, reduced flexion of the surgical knee, and reduced extension of the contralateral knee (P = .04, <.01, and <.01 respectively). Histologically, there was a greater proportion of collagenous tissue and a lower proportion of adipose and synovial tissues in the contracture group than in the noncontracture group; however, the differences were not statistically significant. Cellularity was similar between the 2 groups.
  
  
  CONCLUSIONS
  Longer duration of knee OA, reduced surgical knee flexion, and reduced contralateral, nonsurgical knee extension were associated with KFlC in the OA knee undergoing total arthroplasty. Monitoring bilateral knee range of motion in patients with longer-duration OA could allow earlier intervention, reducing functional loss. Capsular tissue composition analysis may indicate a fibrotic disease process. Further research in which a larger sample size is used will help clarify these novel findings.
authors.affiliation: Department of Medicine, The Ottawa Hospital Rehabilitation Centre, University of Ottawa, Ottawa, ON, Canada(∗). Electronic address: tcampbell@bruyere.org.
authors.forename: Thomas Mark
authors.initials: TM
authors.lastname: Campbell
authors.affiliation: Department of Medicine, The Ottawa Hospital Rehabilitation Centre, University of Ottawa, Ottawa, ON, Canada(†).
authors.forename: Guy
authors.initials: G
authors.lastname: Trudel
authors.affiliation: Department of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada(‡).
authors.forename: Odette
authors.initials: O
authors.lastname: Laneuville
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003286:Contracture / Q000150:complications* / Q000473:pathology* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D017746:Joint Capsule / Q000473:pathology*; D007719:Knee Joint; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000473:pathology* / Q000503:physiopathology; D016059:Range of Motion, Articular