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Pain and Function in Patients After Primary Unicompartmental and Total Knee Arthroplasty
Stein Håkon Låstad Lygre, MSc, PhD1; Birgitte Espehaug, MSc, PhD1; Leif Ivar Havelin, MD, PhD1; Ove Furnes, MD, PhD1; Stein Emil Vollset, MD, DrPH2
1 The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery (S.H.L.L., B.E.), Department of Surgical Sciences (L.I.H., O.F.), Haukeland University Hospital, Møllendalsbakken 11, N-5021 Bergen, Norway. E-mail address for S.H.L. Lygre: stein.lygre@helse-bergen.no
2 The Department of Public Health and Primary Health Care, University of Bergen, N-5020 Bergen, Norway
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Disclosure: In support of their research for or preparation of this work, one or more of the authors received, in any one year, outside funding or grants in excess of $10,000 from the Norwegian Rheumatism Association and the Norwegian Foundation for Health and Rehabilitation. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

Investigation performed at the Norwegian Arthroplasty Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway

Copyright © 2010 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2010 Dec 15;92(18):2890-2897. doi: 10.2106/JBJS.I.00917
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Unicompartmental knee arthroplasty has received renewed interest; however, its short-term advantages over total knee arthroplasty should be weighed against a higher risk of reoperation. Information regarding pain and function after unicompartmental and total knee arthroplasty is therefore needed.


Patient-reported data regarding pain and function were collected, at least two years postoperatively and by way of postal questionnaire, from 1344 patients who were listed on the Norwegian Arthroplasty Register as having had an unrevised primary total knee arthroplasty (972 patients) or a unicompartmental knee arthroplasty (372 patients) for the treatment of arthritis. Outcomes were assessed (with a score of zero indicating the worst possible outcome and a score of 100 indicating the best possible outcome) with use of the five subscales from the Knee Injury and Osteoarthritis Outcome Score, the scores from visual analog scales regarding degree of pain and satisfaction with the surgery, and the change in index score (from preoperative to postoperative) on the EuroQol-5D health-related quality-of-life instrument. We also used all forty-two questions from the Knee Injury and Osteoarthritis Outcome Score as outcome measures. To be regarded as clinically significant, the differences needed to be eight units for the Knee Injury and Osteoarthritis Outcome Score outcomes, ten units for the pain and satisfaction scales, and 0.4 unit for the detailed Knee Injury and Osteoarthritis Outcome Score questions.


Unicompartmental knee implants performed better than total knee implants on the Knee Injury and Osteoarthritis Outcome subscales for "Symptoms" (adjusted mean difference, 2.7; p = 0.04), "Function in Daily Living" (adjusted mean difference, 4.1; p = 0.01), and "Function in Sport and Recreation" (adjusted mean difference, 5.4; p = 0.006). Of the forty-two analyses of the detailed questions, four differences were significant. These differences were in favor of unicompartmental knee arthroplasty, but only the question "Can you bend your knee fully?" reached the level of clinical significance.


We found only small or no differences in pain and function between the scores, at least two years following surgery, of patients who underwent unicompartmental knee arthroplasty and those of patients who underwent total knee arthroplasty; however, patients with unicompartmental knee implants had fewer problems with activities that involved bending the knee.

Level of Evidence: 

Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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