title: Does ipsilateral knee pain improve after hip arthroplasty?
abstract: BACKGROUND
  Intraarticular hip disease is commonly acknowledged as a cause of ipsilateral knee pain. However, this is based primarily on observational rather than high-quality evidence-based studies, and it is unclear whether ipsilateral knee pain improves when hip disease has been treated.
  
  
  OBJECTIVE
  We asked whether (1) hip disease was associated with preoperative ipsilateral knee pain and (2) ipsilateral knee pain would improve after hip arthroplasty.
  
  
  METHODS
  We retrospectively assessed knee pain in 255 patients who underwent hip arthroplasties between 2006 and 2008. The WOMAC pain score of each joint was the primary outcome measure, which was obtained prospectively before surgery and at 3 months and 1 year postoperatively. Of the 255 patients, 245 (96%) had followup data obtained at 3 months or 1 year.
  
  
  RESULTS
  Preoperatively, ipsilateral knee pain was observed more frequently than contralateral knee pain (55% versus 18%). Preoperative ipsilateral knee pain scores were worse than contralateral knee pain scores (mean, 80 versus 95). Ipsilateral knee pain improved at 3 months and 1 year. When compared with the scores for contralateral knee pain at 3 months (95) and 1 year (96), there were no differences between knees.
  
  
  CONCLUSIONS
  Our observations suggest hip disease is associated with ipsilateral knee pain and that it improves after hip arthroplasty. This should be considered during preoperative evaluation for patients with hip and knee pain.
  
  
  METHODS
  Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors: Center for Hip & Knee Replacement, New York-Presbyterian Hospital at Columbia University, PH 1146, PH 11th Floor, 622 W 168th Street, New York, NY 10032, USA.
authors: Wenbao
authors: W
authors: Wang
authors: Jeffrey A
authors: JA
authors: Geller
authors: Jonathan D
authors: JD
authors: Nyce
authors: Jung Keun
authors: JK
authors: Choi
authors: William
authors: W
authors: Macaulay
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D019644:Arthroplasty, Replacement, Hip; D016009:Chi-Square Distribution; D005260:Female; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009519:New York City; D010147:Pain Measurement; D012042:Registries; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult