title: Nonsurgical or Surgical Treatment of ACL Injuries: Knee Function, Sports Participation, and Knee Reinjury: The Delaware-Oslo ACL Cohort Study.
abstract: BACKGROUND
  While there are many opinions about the expected knee function, sports participation, and risk of knee reinjury following nonsurgical treatment of injuries of the anterior cruciate ligament (ACL), there is a lack of knowledge about the clinical course following nonsurgical treatment compared with that after surgical treatment.
  
  
  METHODS
  This prospective cohort study included 143 patients with an ACL injury. Isokinetic knee extension and flexion strength and patient-reported knee function as recorded on the International Knee Documentation Committee (IKDC) 2000 form were collected at baseline, six weeks, and two years. Sports participation was reported monthly for two years with use of an online activity survey. Knee reinjuries were reported at the follow-up evaluations and in a monthly online survey. Repeated analysis of variance (ANOVA), generalized estimating equation (GEE) models, and Cox regression analysis were used to analyze group differences in functional outcomes, sports participation, and knee reinjuries, respectively.
  
  
  RESULTS
  The surgically treated patients (n = 100) were significantly younger, more likely to participate in level-I sports, and less likely to participate in level-II sports prior to injury than the nonsurgically treated patients (n = 43). There were no significant group-by-time effects on functional outcome. The crude analysis showed that surgically treated patients were more likely to sustain a knee reinjury and to participate in level-I sports in the second year of the follow-up period. After propensity score adjustment, these differences were nonsignificant; however, the nonsurgically treated patients were significantly more likely to participate in level-II sports during the first year of the follow-up period and in level-III sports over the two years. After two years, 30% of all patients had an extensor strength deficit, 31% had a flexor strength deficit, 20% had patient-reported knee function below the normal range, and 20% had experienced knee reinjury.
  
  
  CONCLUSIONS
  There were few differences between the clinical courses following nonsurgical and surgical treatment of ACL injury in this prospective cohort study. Regardless of treatment course, a considerable number of patients did not fully recover following the ACL injury, and future work should focus on improving the outcomes for these patients.
  
  
  METHODS
  Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Norwegian Research Center for Active Rehabilitation, Department of Sports Medicine, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway. E-mail address for H. Grindem: hege.grindem@nih.no.
authors.forename: Hege
authors.initials: H
authors.lastname: Grindem
authors.affiliation: Norwegian Research Center for Active Rehabilitation, Department of Orthopaedics, Oslo University Hospital, Kirkeveien 166, 0407 Oslo, Norway.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Eitzen
authors.affiliation: Department of Orthopaedics, Oslo University Hospital, Kirkeveien 166, 0407 Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Engebretsen
authors.affiliation: Department of Physical Therapy, College of Health Sciences, University of Delaware, 540 Sourth College Avenue, Newark, DE 19713.
authors.forename: Lynn
authors.initials: L
authors.lastname: Snyder-Mackler
authors.affiliation: Norwegian Research Center for Active Rehabilitation, Department of Sports Medicine, Norwegian School of Sport Sciences, P.O. Box 4014, Ullevål Stadion, 0806 Oslo, Norway. E-mail address for H. Grindem: hege.grindem@nih.no.
authors.forename: May Arna
authors.initials: MA
authors.lastname: Risberg
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000601:surgery / Q000628:therapy*; D001265:Athletic Injuries / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D007718:Knee Injuries / Q000453:epidemiology*; D008297:Male; D012008:Recurrence; D013177:Sports; D055815:Young Adult
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