title: Pain trajectories identify patients at risk of persistent pain after knee arthroplasty: an observational study.
abstract: BACKGROUND
  Persistent postsurgical pain is a major source of dissatisfaction after knee arthroplasty. Postoperative pain trajectories allow a dynamic view of pain resolution after surgery and might help to identify patients at risk for persistent pain.
  
  
  OBJECTIVE
  In this prospective observational study, we examined the relationship between postoperative pain trajectories and persistent pain, specifically neuropathic pain, at 3 months after knee arthroplasty.
  
  
  METHODS
  Over a 1-year period, all patients undergoing elective unilateral knee arthroplasty for osteoarthritis by one surgeon were invited to participate in the study, provided they had not had prior knee surgery and their American Society of Anesthesiologists grade was 3 or lower; 128 patients fulfilled these criteria. Patients filled in a diary questioning postoperative pain at rest and during mobilization and maximal pain from Day 1 until Day 8 after surgery. At 3 months, the patients were questioned concerning the presence of persistent pain and its nature and intensity using the Douleur Neuropathique 4 [Neuropathic Pain 4] and Brief Pain Inventory questionnaires. At 3 months, 112 of the 128 patients (87%) were successfully contacted.
  
  
  RESULTS
  At 3 months, 47 of the 112 (42%) patients were totally pain free and 65 (58%) reported persistent pain at the surgical site. Among the latter, 12 patients (11%) presented with a neuropathic component and more severe persistent pain. Pain trajectories highlighted higher acute pain scores for maximal pain (from Day 1 until Day 8) and for pain at mobilization (from Day 3 until Day 8) in patients with neuropathic persistent pain (p < 0.05 at all time points compared with the no persistent pain group).
  
  
  CONCLUSIONS
  Postoperative pain trajectories constructed from patient's pain diary suggest that a subgroup of patients who will present with higher pain at 3 months after knee arthroplasty might be identified early in the postoperative period and might benefit from preventative treatment.
  
  
  METHODS
  Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Anesthesiology, St Luc Hospital University, Catholic University of Louvain, Av Hippocrate 10, 1200, Brussels, Belgium, Patricia.Lavandhomme@uclouvain.be.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Lavand'homme
authors.forename: Irina
authors.initials: I
authors.lastname: Grosu
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: France
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Thienpont
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000700:Analgesics / Q000627:therapeutic use; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D017558:Elective Surgical Procedures; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000294:innervation / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009437:Neuralgia / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology*; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000175:diagnosis / Q000188:drug therapy / Q000209:etiology*; D011446:Prospective Studies; D020127:Recovery of Function; D012307:Risk Factors; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000700:Analgesics