title: Time-dependent improvement in functional outcome following Oxford medial unicompartmental knee arthroplasty. A prospective longitudinal multicenter study involving 96 patients.
abstract: OBJECTIVE
  10-year survival rates after unicompartmental knee replacement (UKR) have been up to 97% in single-center studies, but they have been as low as 80% in studies from arthroplasty registers. Few studies have evaluated short-term functional outcome and its improvement with time. We determined the time course of functional outcome as evaluated by the knee injury and osteoarthritis outcome score (KOOS) over the first 2 years after Oxford medial UKR.
  
  
  METHODS
  In a prospective multicenter study, we included 99 unselected knees (96 patients, mean age 65 (51-80) years, 57 women) operated with Oxford medial UKR at 3 hospitals in the southeast of Norway between November 2003 and October 2006. Data were collected by independent investigators preoperatively and at 6 weeks, 3 months, 6 months, 1 year, and 2 years postoperatively. KOOS and range of motion (ROM) were determined at all follow-ups.
  
  
  RESULTS
  Mean KOOS values for pain and activities of daily living were improved already after 6 weeks, and increased between each time point up to 2 years postoperatively. However, no statistically significant improvements were seen after 6 months. Mean active and passive ROM gradually improved up to 2 years after UKR, and were then better than before surgery.
  
  
  CONCLUSIONS
  Most of the expected improvements in pain and function after UKR are achieved within 6 months of surgery. Only minimal improvement can be expected beyond this time.
authors.affiliation: Orthopaedics Department, Martina Hansens Hospital, Baerum, Norway. kjnerhus@gmail.com
authors.forename: Tor Kjetil
authors.initials: TK
authors.lastname: Nerhus
authors.forename: Stig
authors.initials: S
authors.lastname: Heir
authors.forename: Ida
authors.initials: I
authors.lastname: Svege
authors.forename: Inge
authors.initials: I
authors.lastname: Skråmm
authors.forename: Tore
authors.initials: T
authors.lastname: Jervidalo
authors.forename: Jan Erik
authors.initials: JE
authors.lastname: Madsen
authors.forename: Arne
authors.initials: A
authors.lastname: Ekeland
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012086:Reoperation; D013997:Time Factors