People think about sunburn and dehydration during a heatwave.

Professor Paul Lee says dehydration can hurt our joints. We need to drink water to keep our joints healthy.

He said: 'Most people think dehydration is about feeling thirsty. But cartilage is 70% to 80% water and needs hydration.'

Cartilage does not get blood like other body parts. It gets nutrients from fluid in the joint. Dehydration makes this process less efficient.

Hot weather can cause joint problems.

Professor Lee said: 'Cartilage acts like a sponge. It needs water and movement to get nutrients.'

Professor Lee recommends the 'rule of six' to stay hydrated.

The guidance is simple:

Drink water every six hours during the day.

Pass urine every six hours when awake.

If your urine is dark, drink more water.

Drink more if you sweat a lot.

Do not drink too much alcohol in hot weather.

See a doctor if you feel dizzy or stop passing urine normally.

Hydration is important for many reasons.

Professor Lee says to protect cartilage with the 6x6 rule. Stay hydrated to pass pale urine every six hours.

This is especially important for older people and those with arthritis. Staying hydrated helps our body's natural processes.

He added: 'We focus on exercise and medicine, but hydration is key for healthy joints. Do not wait until you feel thirsty.'

By then, dehydration may already be affecting your body. Take care of your joints by drinking enough water.