title: Impact of nervous system hyperalgesia on pain, disability, and quality of life in patients with knee osteoarthritis: a controlled analysis.
abstract: OBJECTIVE
  Refractory, disabling pain associated with knee osteoarthritis (OA) is usually treated with total knee replacement. However, pain in these patients might be associated with central nervous sensitization rather than peripheral inflammation and injury. We evaluated the presence of hyperalgesia in patients scheduled for a total knee replacement due to knee osteoarthritis with refractory pain, and we assessed the impact of pressure pain threshold measurements (PPT) on pain, disability, and quality of life of these patients.
  
  
  METHODS
  Sixty-two female patients were compared with 22 age-matched healthy controls without reported pain for the last year. PPT was measured at the lower extremities subcutaneous dermatomes, over the vastus medialis, adductor longus, rectus femoris, vastus lateralis, tibialis anterior, peroneus longus, iliacus, quadratus lumborum and popliteus muscles and at the supraspinous ligaments from L1-L5, over the L5-S1 and S1-S2 sacral areas and at the pes anserinus bursae and patellar tendon.
  
  
  RESULTS
  Patients with knee OA had significantly lower PPT over all evaluated structures versus healthy control subjects (P<0.001). Lower PPT values were correlated with higher pain intensity, higher disability scores, and with poorer quality of life, except for the role-emotional and general health status. Combined PPT values over the patellar tendon, at the S2 subcutaneous dermatome and at the adductor longus muscle were the best predictors for visual analog scale and Western Ontario and McMaster Universities Osteoarthritis Index pain scores.
  
  
  CONCLUSIONS
  Patients with pain due to osteoarthritis who were scheduled for total knee replacement showed hyperalgesia of nervous system origin that negatively impacted pain, knee functional capacity, and most aspects of quality of life.
authors.affiliation: University of Sao Paulo School of Medicine, Sao Paulo, Brazil. marta@imf.org.br
authors.forename: Marta
authors.initials: M
authors.lastname: Imamura
authors.forename: Satiko Tomikawa
authors.initials: ST
authors.lastname: Imamura
authors.forename: Helena H S
authors.initials: HH
authors.lastname: Kaziyama
authors.forename: Rosa Alves
authors.initials: RA
authors.lastname: Targino
authors.forename: Wu Tu
authors.initials: WT
authors.lastname: Hsing
authors.forename: Luiz Paulo Marques
authors.initials: LP
authors.lastname: de Souza
authors.forename: Martin Mendonça
authors.initials: MM
authors.lastname: Cutait
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
authors.forename: Gilberto Luis
authors.initials: GL
authors.lastname: Camanho
mesh_terms: D000368:Aged; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D006930:Hyperalgesia / Q000209:etiology / Q000523:psychology*; D016014:Linear Models; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000523:psychology*; D010146:Pain / Q000209:etiology / Q000523:psychology*; D017288:Pain Threshold / Q000523:psychology; D011312:Pressure; D011788:Quality of Life