title: Knee extension range of motion and self-report physical function in total knee arthroplasty: mediating effects of knee extensor strength.
abstract: BACKGROUND
  Knee extensor strength and knee extension range of motion (ROM) are important predictors of physical function in patients with a total knee arthroplasty (TKA). However, the relationship between the two knee measures remains unclear. The purpose of this study was to examine whether changes in knee extensor strength mediate the association between changes in knee extension ROM and self-report physical function.
  
  
  METHODS
  Data from 441 patients with a TKA were collected preoperatively and 6 months postoperatively. Self-report measure of physical function was assessed by the Short Form 36 (SF-36) questionnaire. Knee extensor strength was measured by handheld dynamometry and knee extension ROM by goniometry. A bootstrapped cross product of coefficients approach was used to evaluate mediation effects.
  
  
  RESULTS
  Mediation analyses, adjusted for clinicodemographic measures, revealed that the association between changes in knee extension ROM and SF-36 physical function was mediated by changes in knee extensor strength.
  
  
  CONCLUSIONS
  In patients with TKA, knee extensor strength mediated the influence of knee extension ROM on physical function. These results suggest that interventions to improve the range of knee extension may be useful in improving knee extensor performance.
authors: Department of Physiotherapy, Singapore General Hospital, Singapore, Singapore. puayonghao@gmail.com
authors: Yong-Hao
authors: YH
authors: Pua
authors: Peck-Hoon
authors: PH
authors: Ong
authors: Hwei-Chi
authors: HC
authors: Chong
authors: William
authors: W
authors: Yeo
authors: Celia
authors: C
authors: Tan
authors: Ngai-Nung
authors: NN
authors: Lo
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D053587:Arthrometry, Articular; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D016059:Range of Motion, Articular; D020127:Recovery of Function; D057566:Self Report; D013997:Time Factors; D016896:Treatment Outcome