title: Men with early degrees of knee osteoarthritis present functional and morphological impairments of the quadriceps femoris muscle.
abstract: OBJECTIVE
  Quadriceps muscle weakness is common in knee osteoarthritis (OA). Reasons for weakness may include atrophy, reduction in the muscle fibers number, and changes in the muscle activation. It is uncertain when these muscular changes begin to appear. Therefore, the purpose of this study was to determine whether men with early stages of knee OA already had functional and quadriceps muscle morphologic alterations.
  
  
  METHODS
  Forty men were divided into two groups: control group (healthy subjects) and OA group (subjects with knee OA). A biopsy of the vastus lateralis muscle was performed for morphometric analysis. Isokinetic evaluation of knee extensor torque, concentric and eccentric (90 and 180 degrees/sec), was performed simultaneously with vastus lateralis electromyographic activity evaluation.
  
  
  RESULTS
  Significant differences were found in knee extensor torque (P < 0.05) and in normalized root mean square (P < 0.01) during the eccentric contractions (both velocities), with higher values for the control group. No differences were found during concentric contractions. The OA group presented greater values of the minimum diameter of type 1 fibers and greater proportion and relative cross-sectional area of type 2b fibers (P < 0.05).
  
  
  CONCLUSIONS
  Men with early stages of knee OA do not present alterations of concentric strength but had decreased eccentric strength and morphologic quadriceps muscle changes, indicating neuromuscular adaptations.
authors.affiliation: From the Department of Physical Therapy (PRMSS, ABO, SMM, GCL), Department of Gerontology (KG-S, FAV), Department of Medicine (RBMR), Federal University of São Carlos, São Carlos; and Department of Biomechanics, Medicine and Rehabilitation of the Locomotor Apparatus, São Paulo University, Ribeirão Preto, SP, Brazil (ACM-S).
authors.forename: Paula Regina M S
authors.initials: PR
authors.lastname: Serrão
authors.forename: Fernando A
authors.initials: FA
authors.lastname: Vasilceac
authors.forename: Karina
authors.initials: K
authors.lastname: Gramani-Say
authors.forename: Giovanna C
authors.initials: GC
authors.lastname: Lessi
authors.forename: Ana Beatriz
authors.initials: AB
authors.lastname: Oliveira
authors.forename: Rodrigo B M
authors.initials: RB
authors.lastname: Reiff
authors.forename: Ana Cláudia
authors.initials: AC
authors.lastname: Mattiello-Sverzut
authors.forename: Stela M
authors.initials: SM
authors.lastname: Mattiello
mesh_terms: D000328:Adult; D000368:Aged; D004576:Electromyography / Q000379:methods; D006304:Health Status; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000473:pathology / Q000503:physiopathology*; D016059:Range of Motion, Articular; D012016:Reference Values; D019415:Torque