title: Pelvic movement strategies and leg extension power in patients with end-stage medial compartment knee osteoarthritis: a cross-sectional study.
abstract: BACKGROUND
  During movement tasks, patients with medial compartment knee osteoarthritis use compensatory strategies to minimise the joint load of the affected leg. Movement strategies of the knees and trunk have been investigated, but less is known about movement strategies of the pelvis during advancing functional tasks, and how these strategies are associated with leg extension power. The aim of the study was to investigate pelvic movement strategies and leg extension power in patients with end-stage medial compartment knee osteoarthritis compared with controls.
  
  
  METHODS
  57 patients (mean age 65.6 years) scheduled for medial uni-compartmental knee arthroplasty, and 29 age and gender matched controls were included in this cross-sectional study. Leg extension power was tested with the Nottingham Leg Extension Power-Rig. Pelvic range of motion was derived from an inertia-based measurement unit placed over the sacrum bone during walking, stair climbing and stepping.
  
  
  RESULTS
  Patients had lower leg extension power than controls (20-39 %, P < 0.01) and used greater pelvic range of motion during stair and step ascending and descending (P ≤ 0.03, except for pelvic range of motion in the frontal plane during ascending, P > 0.06). Furthermore, an inverse association (coefficient: -0.03 to -0.04; R (2) = 13-22 %) between leg extension power and pelvic range of motion during stair and step descending was found in the patients.
  
  
  CONCLUSIONS
  Compared to controls, patients with medial compartment knee osteoarthritis use greater pelvic movements during advanced functional performance tests, particularly when these involve descending tasks. Further studies should investigate if it is possible to alter these movement strategies by an intervention aimed at increasing strength and power for the patients.
authors.affiliation: Orthopaedic Research, Aarhus University Hospital, Building 10A, Office 5, Tage Hansens Gade 2, 8000, Aarhus C, Denmark, signekierkegaard@hotmail.com.
authors.forename: Signe
authors.initials: S
authors.lastname: Kierkegaard
authors.forename: Peter Bo
authors.initials: PB
authors.lastname: Jørgensen
authors.forename: Ulrik
authors.initials: U
authors.lastname: Dalgas
authors.forename: Kjeld
authors.initials: K
authors.lastname: Søballe
authors.forename: Inger
authors.initials: I
authors.lastname: Mechlenburg
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D010388:Pelvis / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D016138:Walking / Q000502:physiology