The perceived wisdom is that having a very high body mass index (BMI) causes joint problems, such as osteoarthritis. It is true that there is a lot of evidence that people who are overweight or obese have increased incidences of osteoarthritis than those who have a lower BMI. There are some good reasons for this (see below). However what is not true that increased BMI putting additional stress on weight bearing joints causes wear and tear. Joints don't wear out with increased use. In fact the opposite is true - the more you use a healthy joint the better it adapts, strengthens and repairs.

The key word here is HEALTHY. A healthy joint is one that is used regularly in all its ranges of movement. Optimal use increases strength and doesn't cause wear or tear.

It is perfectly possible to have a high BMI and be healthy, fit and very active. Many people who are overweight have a great balanced diet, very healthy joints and a fantastic lifestyle!

Osteoarthritis starts to develop if a joint is repeatedly used outside of its optimal range or only used in a very limited range. If a joint has undergone severe sprain to the supporting ligaments causing instability or subjected to chronic inflammation it may be more prone to abnormal wear and tear. Not using a joint throughout the day, every day may lead to problems. Sometimes there may be anatomical reasons that a joint may develop osteoarthritis - either the joint developed abnormally before birth or in childhood or trauma (fracture) changed the shape and use of the joint. All these factors can occur whatever your BMI.

So why is it also true that a higher BMI is linked to increased risk of osteoarthritis?

There are a few reasons for this

• Weight gain can lead to chronic systemic inflammation which can lead to joint problems and also an increased sensitivity to pain.
• Obesity causes an increase risk of metabolic syndrome and autoimmune conditions such as diabetes
• Excess weight/obesity can be disabling. Compared with healthy-weight people with OA, obese people with OA take more medications, walk more slowly, are less physically active and are at higher risk of becoming disabled.
• Inactivity due to depression or fear avoidance will have negative effects on joints that need to be used regularly to stay healthy. The combination of inflammation and lack of exercise creates a cycle of weight gain, disability, depression and poor health.
• The combination of inflammation and lack of exercise creates a cycle of weight gain, disability, depression and poor health.
• It is true that weight bearing joints are subject to greater stress in obese people, this in itself isn't the problem. The problem with this increase in stress is if the joint is having to adapt its range of movement due to a change in body shape due to obesity.

Advice for those who want to improve joint health - whatever your weight.

• Start to move! Increase your movement a little every day. While walking 10,000 steps a day is a great start, waking (and running) actually only takes a joint through a very limited range.
• Walking on rough ground, over different gradients and on sand all increase the use of weight bearing joints safely.
• Take up aqua exercise if you are concerned about putting stress through your joints. This is a great way of building confidence in your body, safely.
• Standing on one leg for a minute a day and increasing the duration and difficulty over time may sound simplistic but the benefits to weight bearing joints and balance are surprising.
• Yoga and pilates will help with balance, joint flexibility and control in movement.
• Dancing is a fantastic way to use weight bearing joints to their full range and ability.
• If you want to save a joint don't have steroid injections into it! I know, I know steroids work and reduce the pain. But they also cause a rapid acceleration in wear to the joint cartilage not to mention the increase risk of infection that comes with sticking a needle into a sterile joint.

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