title: Total knee arthroplasty after previous knee surgery: expected interval and the effect on patient age.
abstract: BACKGROUND
  With more than 650,000 knee arthroscopies and 175,000 anterior cruciate ligament reconstructions performed annually in the United States, patients presenting for total knee arthroplasty are increasingly likely to have had previous knee surgery. The purpose of this study was to assess the prevalence of previous knee surgery in patients undergoing total knee arthroplasty and to test the hypothesis that patients with previous knee surgery undergo total knee arthroplasty at a younger age.
  
  
  METHODS
  All patients undergoing primary total knee arthroplasty over the study period who consented to enroll in a prospective total joint registry were reviewed. Inclusion criteria included a diagnosis of osteoarthritis or posttraumatic arthritis.
  
  
  RESULTS
  Of 1372 patients in the registry, 1286 met inclusion criteria. Twenty-nine percent had a history of knee surgery, and significantly more men (39%) than women (24%) had a history of knee surgery (p &lt; 0.0001). Patients with previous knee surgery were significantly younger (p &lt; 0.0001) at total knee arthroplasty; the mean age (and standard deviation) was 59 ± 10 years for patients with previous knee surgery compared with 66.6 ± 10.4 years for patients without previous knee surgery. Patients with a history of ligament reconstruction underwent total knee arthroplasty at a significantly younger age (p &lt; 0.0001) than patients with a history of other knee surgery; the mean age (and standard deviation) was 50.2 ± 9.1 years for patients with a history of ligament reconstruction and 59.9 ± 9.6 years for patients with a history of other knee surgery. Among patients who had not undergone previous knee surgery, women underwent total knee arthroplasty at a significantly younger age (p &lt; 0.001) than men; the mean age (and standard deviation) was 65.4 ± 10.3 years for women and 69.3 ± 10 years for men. However, there was no difference in age between the sexes in those with previous knee surgery; the mean age (and standard deviation) was 58.6 ± 10.1 years for women and 59.6 ± 9.8 years for men. The average interval (and standard deviation) from previous knee surgery to total knee arthroplasty is 13.1 ± 12.6 years, longer in men (17.7 ± 13.8 years) than in women (9.1 ± 9.8 years) (p &lt; 0.0001).
  
  
  CONCLUSIONS
  Patients with previous knee surgery undergo total knee arthroplasty at a significantly younger age than patients without previous knee surgery, especially men and patients with a history of ligament reconstruction. This may be a factor in the rising demand for total knee arthroplasty. Future investigation to identify those at risk for early total knee arthroplasty after knee surgery and to develop methods to delay or to prevent the need for future total knee arthroplasty in these patients is warranted.
  
  
  METHODS
  Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 14532 South Outer Forty Drive, Chesterfield, MO 63017.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Brophy
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 14532 South Outer Forty Drive, Chesterfield, MO 63017.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Gray
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 14532 South Outer Forty Drive, Chesterfield, MO 63017.
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Nunley
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 14532 South Outer Forty Drive, Chesterfield, MO 63017.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Barrack
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 14532 South Outer Forty Drive, Chesterfield, MO 63017.
authors.forename: John C
authors.initials: JC
authors.lastname: Clohisy
mesh_terms: D000367:Age Factors; D000368:Aged; D001168:Arthritis / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000601:surgery; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011379:Prognosis; D011446:Prospective Studies; D024162:Second-Look Surgery / Q000706:statistics & numerical data; D017678:Sex Distribution; D013997:Time Factors