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Knee replacement surgery significantly safer

Close-up view of human knee x-ray

Close-up view of human knee x-ray

Press release issued: 8 July 2014

Mortality rates in the first 45-days following knee replacement surgery have fallen dramatically since 2003, according to a National Joint Registry for England, Wales and Northern Ireland (NJR) study led by the University of Bristol.

Published in The Lancet today (8 July 2014), a team of researchers have analysed NJR data on death after knee replacement and found that:

  • The risk of dying after knee replacement surgery has almost halved from 0.37 per cent in 2003 to 0.2 per cent in 2011 (146 patients).
  • Older men with illnesses such as liver, cardiac or renal disease are at the highest risk of death after knee surgery. As a result, doctors can take greater care with and provide careful counselling to these patients. For example, their recovery might be improved if they were cared for in high dependency units.
  • Use of thromboprophylactic agents (treatments to prevent blood clots) is not associated with lower death rates after knee replacement and use of these agents could be re-evaluated to examine the risks and benefits.
  • Being overweight, but not obese, is associated with the lowest risk of death – even lower than those with normal weight. This challenges the concept of what is an ideal weight in this group of patients.
  • Partial knee replacements are associated with a lower risk of death than total knee replacements but patients and surgeons need to consider other factors before choosing the most appropriate procedure. These other important factors include revision/reoperation rates, risk of complication, readmission as well as relief from pain and poor mobility.

Professor Ashley Blom from the University of Bristol who led the team that undertook this work on behalf of the National Joint Registry said: “It is excellent news the risk of death after both hip and knee replacement has fallen so dramatically since 2003. It is interesting that measures to decrease clot formation after knee replacement are not associated with a decrease in the risk of death. In light of this, we need to further evaluate the risk and benefits of these treatments.

“We have also shown an association between lower risk of death and being overweight, but not obese. This challenges the concept of what constitutes an ideal body mass index in older patients with osteoarthritis.

“It is not surprising that partial knee replacements are associated with a lower risk of death as they are smaller operations than replacing the entire knee. These data add further support to their use.”

Mary Cowern, NJR patient representative who has undergone three knee surgeries for arthritis since 1996, said: “This research outlines key areas for conversation between a potential knee replacement patient and their surgeon. From my own experience, I know how valuable an open discussion is – it can really help you to understand the risks, benefits and what role you have to play in your own recovery. Evidence like this offers surgeons and patients an opportunity to start a meaningful dialogue within a shared decision making framework - where the surgeon and the patient can work together to make a decision about treatment.”

Today’s paper is published alongside another study in The Lancet using NJR data, looking at adverse outcomes after partial and total knee replacement surgery.

This study, carried out by the Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences at the University of Oxford, also supports the view that partial knee replacement surgery should continue to be offered as a treatment option to patients. In these findings, partial knee replacement was shown to be associated with higher revision/reoperation rates but lower occurrences of complication, readmission to hospital and death following surgery.

Elaine Young, Director of operations for the National Joint Registry, concluded: “The NJR is delighted to see these published papers. Not only do they highlight the importance of NJR data in research but the relevance of high quality, peer reviewed literature in influencing clinical practice and helping to improve patient outcomes for joint replacement surgery.”

Paper: 45-day mortality after 467 779 knee replacements for osteoarthritis from the National Joint Registry for England and Wales: an observational study, Linda P Hunt PhD, Prof Yoav Ben-Shlomo, Emma M Clark, Prof Paul Dieppe, Andrew Judge, Prof Alex J MacGregor, Prof Jon H Tobias, Kelly Vernon, Prof Ashley W Blom, on behalf of the National Joint Registry for England and Wales, The Lancet, 8 July 2014.

Further information

Related papers:

Adverse outcomes after total and unicompartmental knee replacement in 101 330 matched patients: a study of data from the National Joint Registry for England and Wales. Lancet (in print).

90-day mortality after 409, 096 total hip replacements for osteoarthritis, from the National Joint Registry for England and Wales: a retrospective analysis.

About the National Joint Registry for England, Wales and Northern Ireland

Established in 2002, the NJR monitors the performance of hip, knee, ankle, elbow and shoulder joint replacements to improve clinical outcomes for the benefit of patients, clinicians and industry. The registry collects relevant, high quality data in order to provide quality, robust evidence to support decision-making in regard to patient safety, standards in quality of care and overall cost effectiveness in joint replacement surgery. It also supports and enables research to maximise the value of the information it holds, now more than 1.6 million records, and collaborates internationally to foster greater knowledge and understanding. Find out more at

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