Why do I feel dizzy when I stand up?


Q. Why is it that whenever I bend down and then stand up suddenly I feel dizzy?I have had a normal ECG and blood test. I am a 58-year-old man, a smoker, slim build and reasonably fit. I work in an office and walk for two to three hours a day.

A. You feel dizzy when you stand up quickly after bending down because your blood pressure is unable to pump enough blood to your brain. When your brain is short of blood and oxygen, it makes you feel dizzy. At the same time you may feel a pounding in your head, as your body tries to compensate by letting more blood get to your brain. The technical name for this problem is postural hypotension, which means that your blood pressure drops when you stand up. This can be a side effect of some blood pressure medications, but many healthy people notice this kind of dizziness as they get older. The problem may also be worse if you don't drink enough fluids during the day, or if your salt intake is too low. You should get your blood pressure checked. Smoking will not help the problem, as it makes blood vessels less responsive.


Q. My left knee has started to give me trouble, especially when I am squatting in the gym and going up and down stairs. If I bend the knee, there is a gently crunching and grinding sound behind the kneecap. I am 22 years old and healthy, although slightly overweight.

A. This is likely to be chondromalacia patellae. The patella is the kneecap, and the back surface of it is lined with cartilage. The cartilage acts as a buffer, which allows the kneecap to slide over the front of the knee joint whenever the knee is bent. The cartilage behind the kneecap is supposed to be firm and smooth. If, for unknown reasons, it becomes softer than normal, the smooth surface becomes rough and irregular. The grinding noise is caused by the rough cartilage rubbing against the knee bones. The best treatment is a combination of rest, painkillers and physiotherapy, to maintain the strength of the muscles around the knee joint. The Arthritis Research Campaign publishes a comprehensive booklet about chondromalacia patellae ( www.arc.org.uk; 0870 850 5000).

Please send your questions and suggestions to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax 020-7005 2182; or e-mail health@independent.co.uk. Dr Kavalier regrets that he is unable to respond personally to questions.

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