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How Does Obesity Affect Your Risk Of OA Knee Pain

2nd May 2019

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Obesity has been known to be a serious health problem for many years, but the impact that being overweight can have on your knees is not always recognised. Seriously obese people are fourteen times more likely to develop osteoarthritis (OA) of the knee than people whose weight is within healthy parameters, so it follows that maintaining a healthy weight can reduce your risk of knee pain due to this disease.

What is osteoarthritis?

In OA, the protective cartilage that covers the ends of the bones breaks down and this can cause pain and swelling. There may also be problems moving the joint and it may become inflamed. The cartilage should normally cushion the joint and prevent the bones from rubbing together, but when the cartilage breaks down, the bones start to rub against each other causing the pain that is typical of the condition.

Although the precise cause of OA is not known, there are certain factors that increase the risk of developing it. There is an increased risk of developing the condition following injury to the joint and as you grow older, but the major avoidable cause is obesity.

Excess weight puts increased strain on the knees which causes cartilage damage to occur. Although osteoarthritis is often described as a disease of wear and tear, not everyone develops it as they age and everyone uses their knees to some extent. There is some evidence that the condition may run in families but this is not definitive. Previous knee injury appears to be a predisposing factor but being overweight or obese can cause irreversible damage to the knee joints and is generally avoidable.

In the UK, osteoarthritis is currently the fastest growing cause of disability, possibly because the number of people who are overweight or obese is also increasing so quickly.


A survey conducted in 2016 revealed that 26 percent of adults in England were obese with a body mass index (BMI) of 30 or above and a further 35 percent were overweight which means they have a BMI of between 25 and 30. More men than women were obese and those aged between 45 and 74 had the highest levels of obesity.

There are many health problems associated with obesity including heart disease, high blood pressure, type 2 diabetes and degenerative arthritis. People with obesity are four times more likely to get knee osteoarthritis than they are to develop type-2 diabetes or high blood pressure. Whilst some conditions such as diabetes and high blood pressure can be improved considerably by losing weight and there are treatments available that can control them quite well, the situation is different with osteoarthritis.

The changes to the cartilage that are caused by osteoarthritis cannot be repaired so the condition is irreversible. Knee pain and other symptoms due to the condition can, however, be managed through exercise combined with losing weight. In addition to obesity increasing the strain on the knee joints, excess fat also causes inflammation that can make symptoms worse. Losing weight has been shown not only to reduce pain, but also to improve mobility and physical function.

Losing weight in knee osteoarthritis

Obese or overweight people will gain optimum benefit from losing ten percent of their body weight. This will not only improve their symptoms, it will also promote health generally. Eating a healthy diet that includes plenty of fresh fruit and vegetables will help with weight loss. It is also important to incorporate some exercise whilst losing weight because this will help to maintain muscle. Losing excess weight also helps to manage or prevent cardiovascular disease and type 2 diabetes, both of which have been linked with osteoarthritis.

Dietary factors to consider in osteoarthritis

Try to have a minimum of one and preferably two portions of oily fish each week, for example, salmon, tuna (not tinned), mackerel or sardines. These contain long-chain omega-3 polyunsaturated fatty acids which have anti-inflammatory properties that are thought to be beneficial for people with OA. Fish oil capsules could be tried as a substitute if you are unable to eat oily fish.

Vitamin D is important for the health of bone and cartilage. It is also thought to improve balance and muscular strength. In the UK we get most of our vitamin D from sunlight between April and October and most people only consume a small amount in their diet. You should try to be exposed to sunlight for ten to fifteen minutes each day in the summer. A daily supplement of vitamin D, particularly during the winter, can help to keep up the level you need throughout the year. Keeping your weight at a healthy level can also make it easier for your body to access vitamin D because it is stored in fat.

Vitamin K is thought to influence osteoarthritis because of its role in the manufacture of bone and cartilage. Whilst its benefit in OA is not proven, it has been suggested that increasing the amount of vitamin K for anyone deficient might be beneficial so it is important that is included as part of a healthy and balanced diet. Vitamin K is present in small amounts in some oils and fats such as olive oil and margarine which may also help it to be absorbed from food.

Although avoidance of certain foods such as vegetables such as potatoes, tomatoes and other nightshade vegetables or dairy products may be helpful in rheumatoid arthritis, food avoidance does not appear to produce any benefits in OA. Similarly, there is no evidence that dietary supplements such as chondroitin, glucosamine, turmeric or rose hip are beneficial in OA, although people whose diet is restricted may benefit from a multivitamin and mineral supplement.

Exercise and knee osteoarthritis

Simple exercises combined with reaching or maintaining a healthy weight can help to reduce pain and prevent the development of further symptoms. Leg raises, step ups, knee squats and leg stretches can all be effective in maintaining mobility and easing pain. These exercises can all be done simply at home by most people. Sit/stands where you stand up from a chair and then sit back down in a controlled way without using your hands are good for mobility and balance. As you improve, you can use a lower chair and increase the number of times the exercise is repeated.

Obesity and knee osteoarthritis

The number of people with obesity is increasing in the UK and people are living longer too. Both ageing and obesity are major risk factors for the development of osteoarthritis so it follows that the costs to the health service are likely to rise substantially too.

Knee replacements are likely to fail sooner in people who are obese than in those of a healthy weight. Symptoms are also less likely to be improved significantly by surgery when the patient is obese; the heavier they are, the less improvement will be experienced.

Women who are very obese are nineteen times more likely to need a knee replacement than women who are a healthy weight.

Research has shown that exercise combined with modest weight loss can be effective in reducing pain and improving mobility. It can also help patients to regain the ability to carry out everyday activities that they may have been unable to manage whilst they were obese.

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