title: Strength and voluntary activation of the quadriceps femoris muscle at different severities of osteoarthritic knee joint damage.
abstract: OBJECTIVE
  Improvements of quadriceps motor deficits represent a major therapeutical target in knee osteoarthritis (OA). In the present study, we investigated changes in quadriceps function at different stages of osteoarthritic cartilage damage.
  
  
  METHODS
  Measurements of quadriceps voluntary activation (VA) and maximum voluntary contraction (MVC) were performed by a twitch interpolation technique and the total muscular capacity (TMC) was calculated as the ratio of MVC and VA. We assessed 68 patients (56.7+/-9.5 years) with stage II and 154 patients (65.6+/-6.0 years) with stage IV chondropathy. As controls, we used 85 age related healthy subjects (58.1+/-8.7 years).
  
  
  RESULTS
  While TMC was significantly lower in stage IV (90.6+/-43.7 Nm) than in stage II chondropathy (109.6+/-51.0) there were no differences in the MVCs between both groups. Quadriceps VA was even higher in stage IV (77.2+/-13.2%) than in stage II chondropathy (70.8+/-16.0%). In the controls, MVC, VA and TMC were significantly higher than in both OA groups.
  
  
  CONCLUSIONS
  We assume that a decrease of TMC might occur within the course of OA and, in consequence, VA increases to maintain quadriceps MVC.
authors.affiliation: Neuromuscular Research Group, Department of Orthopaedics, Otto-von-Guericke University, Leipziger Street 44, D-39120 Magdeburg, Germany. geza.pap@medizin.uni-magdeburg.de
authors.forename: Géza
authors.initials: G
authors.lastname: Pap
authors.forename: Andreas
authors.initials: A
authors.lastname: Machner
authors.forename: Friedemann
authors.initials: F
authors.lastname: Awiszus
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D013848:Thigh / Q000502:physiology; D014836:Volition / Q000502:physiology