title: Moderate varus/valgus malalignment after total knee arthroplasty has little effect on knee function or muscle strength.
abstract: OBJECTIVE
  Postoperative muscle strength and component alignment are important factors affecting functional results after total knee arthroplasty (TKA). We are not aware of any studies that have investigated the relationship between them. We therefore investigated whether coronal malalignment of the mechanical axis and/or of individual implant components would affect knee muscle strength and function 1 year after TKA surgery.
  
  
  METHODS
  We included 120 consecutive osteoarthritis (OA) patients admitted for TKA. Preoperative active range of motion (ROM) of the knee, patient age, sex, and BMI were recorded and the Knee Society score (KSS) and knee joint extensor/flexor muscle strength were assessed. At 1-year follow-up, the mechanical and coronal component alignment was measured from a postoperative long standing radiograph, and ROM, KSS, and muscle strength measurements were taken in 91 patients. Functional outcome and muscle strength measurements were compared between normally aligned and malaligned TKA groups.
  
  
  RESULTS
  29 of 91 TKAs were malaligned, i.e. they deviated more than 3° from the neutral mechanical axis. 18 femoral components and 15 tibial components were malaligned. Before surgery, the malaligned and normally aligned groups were similar regarding sex distribution, BMI, ROM, KSS, and muscle strength. At the 1-year follow-up, the differences between the groups regarding knee joint function and muscle strength were small, not statistically significant, and barely clinically relevant.
  
  
  CONCLUSIONS
  Moderate varus/valgus malalignment of the mechanical axis or of individual components has no relevant clinical effect on function or muscle strength 1 year after TKA surgery.
authors.affiliation: a 1 Department of Orthopaedics , Lithuanian University of Health Sciences, Kaunas, Lithuania.
authors.forename: Justinas
authors.initials: J
authors.lastname: Stucinskas
authors.affiliation: b 2 Department of Clinical Sciences and Department of Orthopaedics , Lund University and Lund University Hospital, Lund, Sweden .
authors.forename: Otto
authors.initials: O
authors.lastname: Robertsson
authors.affiliation: a 1 Department of Orthopaedics , Lithuanian University of Health Sciences, Kaunas, Lithuania.
authors.forename: Aurimas
authors.initials: A
authors.lastname: Sirka
authors.affiliation: a 1 Department of Orthopaedics , Lithuanian University of Health Sciences, Kaunas, Lithuania.
authors.forename: Aleksej
authors.initials: A
authors.lastname: Lebedev
authors.affiliation: b 2 Department of Clinical Sciences and Department of Orthopaedics , Lund University and Lund University Hospital, Lund, Sweden .
authors.forename: Hans
authors.initials: H
authors.lastname: Wingstrand
authors.affiliation: a 1 Department of Orthopaedics , Lithuanian University of Health Sciences, Kaunas, Lithuania.
authors.forename: Sarunas
authors.initials: S
authors.lastname: Tarasevicius
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D017760:Bone Malalignment / Q000150:complications* / Q000209:etiology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D008297:Male; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000601:surgery; D016059:Range of Motion, Articular / Q000502:physiology