title: Relationship between leg extensor muscle strength and knee joint loading during gait before and after total knee arthroplasty.
abstract: OBJECTIVE
  The aim of the present study was to evaluate an isometric maximal voluntary contraction (MVC) force of the leg extensor muscles and its relationship with knee joint loading during gait prior and after total knee arthroplasty (TKA).
  
  
  METHODS
  Custom-made dynamometer was used to assess an isometric MVC force of the leg extensor muscles and 3-D motion analysis system was used to evaluate the knee joint loading during gait in 13 female patients (aged 49-68 years) with knee osteoarthritis. Patients were evaluated one day before, and three and six months following TKA in the operated and non-operated leg.
  
  
  RESULTS
  Six months after TKA, MVC force of the leg extensor muscles for the operated leg did not differ significantly as compared to the preoperative level, whereas it remained significantly lower for the non-operated leg and controls. The knee flexion moment and the knee joint power during mid stance of gait was improved six months after TKA, remaining significantly lowered compared with controls. Negative moderate correlation between leg extensor muscles strength and knee joint loading for the operated leg during mid stance was noted three months after TKA.
  
  
  CONCLUSIONS
  The correlation analysis indicates that due to weak leg extensor muscles, an excessive load is applied to knee joint during mid stance of gait in patients, whereas in healthy subjects stronger knee-surrounding muscles provide stronger knee joint loading during gait.
  
  
  METHODS
  III (correlational study).
authors.affiliation: Institute of Exercise Biology and Physiotherapy, University of Tartu, 5 Jakobi Street, 51014 Tartu, Estonia. Electronic address: Doris.Vahtrik@ut.ee.
authors.forename: Doris
authors.initials: D
authors.lastname: Vahtrik
authors.affiliation: Institute of Exercise Biology and Physiotherapy, University of Tartu, 5 Jakobi Street, 51014 Tartu, Estonia.
authors.forename: Helena
authors.initials: H
authors.lastname: Gapeyeva
authors.affiliation: Institute of Exercise Biology and Physiotherapy, University of Tartu, 5 Jakobi Street, 51014 Tartu, Estonia.
authors.forename: Jaan
authors.initials: J
authors.lastname: Ereline
authors.affiliation: Institute of Exercise Biology and Physiotherapy, University of Tartu, 5 Jakobi Street, 51014 Tartu, Estonia.
authors.forename: Mati
authors.initials: M
authors.lastname: Pääsuke
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D005684:Gait / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007719:Knee Joint / Q000502:physiology*; D035002:Lower Extremity / Q000502:physiology*; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery; D011184:Postoperative Period; D057234:Preoperative Period; D016474:Weight-Bearing / Q000502:physiology*
keywords: Gait; Isometric muscle contraction; Knee joint loading; Knee osteoarthritis; Total knee arthroplasty