Your excuse for not going jogging may have just been debunked.
Experts say running is not actually bad for the knees - a view held by many who love to pound the pavements.
Studies show there is no link between running and osteoarthritis, and the exercise may even strengthen cartilage.
A book called Running Science says 'couch potatoes' have around a 45 per cent greater risk of osteoarthritis compared to those who run, reports Daily Mail.
It states that runners place eight times their body weight on to each leg with every step.
Although that is three times as much as when walking, we take wider strides when running, so there is reduced contact time with the ground.
This means the pressure on the knees is broadly similar.
The book's consultant editor, Professor John Brewer, of St Mary's University in London, said runners should increase intensity of the exercise gradually, wear the right shoes and run on different terrains.
He said: 'The human body is designed to run... although the knees will be under stress when running, the body will adapt to this stress and develop cartilage, muscles, tendons and ligaments that are stronger as a result of running - protecting the knee rather than damaging it.'
Running Science, published earlier this week, says that damage to joints is a 'common excuse' for not running.
However, a chapter by independent physiotherapist Anna Barnsley states: 'The good news is that the converse appears to be true.'
She cites studies showing that although runners develop bony growths in their knees, there is no evidence of narrowing of the joint space, which would indicate degeneration.
The agony of osteoarthritis is caused when cartilage is no longer there to cushion the joints - but the book states that running probably increases cartilage.
That could be because exercise helps people lose fat, which can damage cartilage.
Running also prompts blood flow and cell regeneration in the knees.
The advice follows a study by Baylor College of Medicine in the US, which analysed knee X-rays of 2,683 participants.
The study found that 22.8 per cent of those who had been runners had signs of knee osteoarthritis, compared to 29.8 per cent of non-runners.
Running Science also noted that some runners may have a genetic predisposition to osteoarthritis - meaning exercise is not necessarily to blame.