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Rapid response to:


Recommended physical activity and all cause and cause specific mortality in US adults: prospective cohort study

BMJ 2020; 370 doi: (Published 01 July 2020) Cite this as: BMJ 2020;370:m2031

Rapid Response:

Exercise is good for you. So is NICE guideline 157 if you wear out your knees keeping fit.

Dear Editor

Good news for the government and the public: exercise really is good for us: data from half a million Americans reports the impact of strength and conditioning exercise: a 40% reduction in the risk of death from cardiac, respiratory or malignant causes[1]. This observational dataset is both statistically and clinically important, suggesting that for close to zero healthcare spending, a substantial societal health gain can be made.

In more good news, NICE guideline 157 published last month may have a similar impact for those whose knees are worn out by their exercise regime[2]. NICE recommends that all eligible patients be offered the choice of partial or unicompartmental knee replacement (UKR), which also offers a 40% reduction in the risk of dying at 10 years (14% mortality following UKR vs 23% following total knee replacement (TKR) according to the Australian National Joint Registry)[3]. The National Joint Registry of England and Wales last published this statistic back in 2012 (8% mortality following UKR vs 18% following TKR at 7 years postop). While UKR isn’t ‘no cost’, last year a large RCT confirmed it to be cheaper and more effective than TKR[4]. It is also now performed routinely in a day case setting[5].

So if lockdown exercise keeps us healthy but wears our knees away, a small safe and effective intervention is available. About half of the 100,000 knee replacements could be done this way[6], saving thousands of lives and perhaps £50m a year.

1. Zhao, M., et al., Recommended physical activity and all cause and cause specific mortality in US adults: prospective cohort study. BMJ, 2020. 370: p. m2031.
2. Joint replacement (primary): hip, knee and shoulder NICE guideline [NG157]. 2020.
3. AOANJRR, Mortality following Hip and Knee Arthroplasty. 2018: Adelaide 2018. p. 8-9.
4. Beard, D.J., et al., The clinical and cost-effectiveness of total versus partial knee replacement in patients with medial compartment osteoarthritis (TOPKAT): 5-year outcomes of a randomised controlled trial. Lancet, 2019.
5. Kort, N.P., Y.F. Bemelmans, and M.G. Schotanus, Outpatient surgery for unicompartmental knee arthroplasty is effective and safe. Knee Surg Sports Traumatol Arthrosc, 2015.
6. Willis-Owen, C.A., et al., Unicondylar knee arthroplasty in the UK National Health Service: An analysis of candidacy, outcome and cost efficacy. Knee, 2009.

Competing interests: No competing interests

06 July 2020
Justin P Cobb
Professor of Orthopaedic Surgery
Imperial College
Sir Michael Uren Biomedical Engineering Research Hub, White City Campus, 80-92 Wood Lane London W12 0BZ