The bind you are actually in
You have been told to lose weight for your knees. Possibly several times, possibly by someone who did not ask what you had already tried.
The instruction is not wrong. It is incomplete, because it skips the part you live with: the knee hurts, so you move less, and moving less makes weight loss harder.
What follows is the guideline’s actual wording, the real source of the figure you have heard about pressure on the knee, and how research eligibility works.
How many people this affects in the UK
Over 10 million people in the UK have osteoarthritis, according to Versus Arthritis in The State of Musculoskeletal Health 2024. Roughly 1 in 6 people in the UK live with arthritis of some kind.
An estimated 5.4 million people have knee osteoarthritis and an estimated 3.2 million have hip osteoarthritis. Versus Arthritis also estimates that 8.75 million people over 45 have sought treatment for osteoarthritis.
The NHS calls osteoarthritis the most common type of arthritis in the UK, most often affecting the knees, hips and small joints of the hands. That page was last reviewed on 20 March 2023.
What NICE NG226 calls core treatment
NICE published NG226, “Osteoarthritis in over 16s: diagnosis and management”, on 19 October 2022.
Recommendation 1.2.2 says “the core treatments for the condition are therapeutic exercise and weight management (if appropriate), along with information and support.”
Two details get lost when that sentence is summarised in a consultation. Therapeutic exercise is named first. Weight management carries the qualifier “if appropriate”.
Exercise, including the recommendation about pain
Recommendation 1.3.1 has no qualifier attached: “For all people with osteoarthritis, offer therapeutic exercise tailored to their needs (for example, local muscle strengthening, general aerobic fitness).”
Recommendation 1.3.2 says to consider supervised therapeutic exercise sessions.
Recommendation 1.3.3 is the one almost nobody has had read to them. NICE advises telling people that joint pain may increase when they start therapeutic exercise, and explaining that “doing regular and consistent exercise, even though this may initially cause pain or discomfort, will be beneficial for their joints; long-term adherence to an exercise plan increases its benefits by reducing pain and increasing functioning and quality of life.”
So the guideline expects early discomfort and tells clinicians to say so. That is not the same as “stop if it hurts”.
Versus Arthritis groups the recommended movement into range of movement exercises, strengthening exercises and aerobic exercise. In practice that covers:
- range of movement exercises
- strengthening using light weights
- strengthening using resistance bands
- exercising in water
- walking or cycling
- swimming or an exercise bike
What the guideline says about weight, in full
Recommendation 1.3.5 applies to people with osteoarthritis living with overweight or obesity. It says to advise them that weight loss will improve quality of life and physical function and reduce pain, and to support them to choose a weight loss goal.
It then says: “explain that any amount of weight loss is likely to be beneficial, but losing 10% of their body weight is likely to be better than 5%.”
Notice what is not there. No target weight, no BMI figure, no threshold below which effort stops counting. 5% is worth having, and 10% is better than 5%.
The four pounds per pound claim, and where it came from
You have probably heard that losing one pound takes four pounds of pressure off the knee. One influential study is the source of that figure.
Messier and colleagues published “Weight loss reduces knee-joint loads in overweight and obese older adults with knee osteoarthritis” in Arthritis and Rheumatism in July 2005, volume 52, issue 7, pages 2026 to 2032. 142 older adults living with overweight or obesity and with knee osteoarthritis completed an 18 month diet and exercise weight loss programme, with an average body weight loss of about 2 percent. The researchers measured compressive load on the knee during walking and found that each pound of weight lost corresponded to roughly a four pound reduction in per-step knee joint load. The lead author was quoted at the time saying that for someone losing 10 pounds, each knee would be subject to 48,000 pounds less compressive load per mile walked.
Now the caveat that rarely travels with the number. This was a single US cohort study, and what it measured was joint load during walking. It did not show that weight loss slows osteoarthritis. The study’s own investigator said at the time that no studies then available showed weight loss slowing progression of the disease, only that it reduced load through the joint.
One study, about mechanics, in one group of people. Worth knowing, and not a physical law.
What NG226 does not recommend
Guidelines get read for what they endorse. The exclusions are rarely reported.
NG226 does not recommend the following for osteoarthritis:
- acupuncture
- TENS or electrotherapy
- glucosamine
- routine intra-articular hyaluronan injections
If you are paying for any of these, that is where the national guideline stands.
The same weight that loads the knee sits behind other conditions that often go unnoticed: up to 1 in 3 people in the UK have early-stage fatty liver disease, covered in our article on MASH and fatty liver disease without alcohol, and there is a separate piece on what happens when statins are not enough.
Where clinical research fits, and how eligibility works
Clinical research is one option people look at once the standard advice has been tried.
Studies in this area typically compare an investigational treatment against a placebo. Eligibility is set by the pharmaceutical sponsor’s protocol, not by the clinic running the study. A screening visit is what determines whether someone is eligible. Some studies exclude people with type 1 or type 2 diabetes, or people who have had a knee replacement in the affected knee. Participation is voluntary and can be stopped at any point.
Before consenting you get a Participant Information Sheet to read and time to ask the study team questions. Study-related assessments and monitoring are provided as part of the trial, reasonable travel costs may be reimbursed, and compensation for time may be available.
Frequently asked questions
Does NICE actually say I have to lose weight for my knee osteoarthritis?
No. NG226 recommendation 1.2.2 names weight management as a core treatment with the qualifier “if appropriate”, and names therapeutic exercise first. Recommendation 1.3.5 applies to people living with overweight or obesity and says to advise that weight loss will reduce pain and improve physical function, and to support the person to choose their own goal.
How much weight does NICE say to lose?
NG226 does not give a target weight or BMI. Recommendation 1.3.5 says to “explain that any amount of weight loss is likely to be beneficial, but losing 10% of their body weight is likely to be better than 5%.” The goal itself is chosen by the person, with support.
Is it true that losing 1lb takes 4lb of pressure off my knee?
One study found that. Messier and colleagues, publishing in Arthritis and Rheumatism in 2005, measured knee joint load during walking in 142 older adults with knee osteoarthritis and found each pound lost corresponded to roughly a four pound reduction in per-step load. It measured joint load, not whether osteoarthritis progressed more slowly.
Should I stop exercising if my knee hurts more when I start?
NG226 recommendation 1.3.3 anticipates exactly this. It advises telling people that joint pain may increase when therapeutic exercise starts, and that regular consistent exercise will be beneficial for their joints even though it may initially cause pain or discomfort. Discuss any new or severe pain with your GP or physiotherapist.
Can I join a knee osteoarthritis trial if I have had a knee replacement?
Some studies exclude people who have had a knee replacement in the affected knee, and some exclude people with type 1 or type 2 diabetes. Criteria are set by the study sponsor’s protocol and differ between studies. A screening visit is what confirms whether you are eligible.
About Panthera
Panthera Biopartners is the UK’s largest Site Management Organisation for commercial clinical trials, with seven clinics in Glasgow, Enfield, Keele, Preston, Rochdale, Sheffield and York. Panthera runs studies for pharmaceutical sponsors and does not design protocols, own investigational products or set eligibility criteria, and does not conduct first-in-human studies. You can read what taking part involves on the knee pain and weight management clinical trial page.
Disclaimer
Not medical advice. This article is general information about osteoarthritis and national guidance, not a substitute for advice from a qualified healthcare professional who knows your history.
Conflicts and affiliations. Panthera Biopartners runs clinical trials, including studies relating to knee pain and weight management. Whether a study is suitable is a decision for you, your own clinician and the study team at a screening visit.
