# What causes bent knees to ache?

**URL:** <https://boards.straightdope.com/t/what-causes-bent-knees-to-ache/839190>\
**Category:** Factual Questions\
**Created:** [August 25, 2019, 12:10am UTC](https://boards.straightdope.com/t/what-causes-bent-knees-to-ache/839190 "2019-08-25T00:10:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Son\_of\_a\_Rich](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/son_of_a_rich/32/5439_2.png) [@Son\_of\_a\_Rich](https://boards.straightdope.com/u/Son_of_a_Rich)\
**Post date:** [August 25, 2019, 12:10am UTC](https://boards.straightdope.com/t/what-causes-bent-knees-to-ache/839190/1 "2019-08-25T00:10:47Z")

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I could go a lot further on my motorcycle if after a few hours my knees didn’t start aching. What’s the cause of the hurt?

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**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\
**Post date:** [August 25, 2019, 1:05am UTC](https://boards.straightdope.com/t/what-causes-bent-knees-to-ache/839190/2 "2019-08-25T01:05:28Z")

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WAG. The vibration maybe?

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**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\
**Post date:** [August 27, 2019, 12:14am UTC](https://boards.straightdope.com/t/what-causes-bent-knees-to-ache/839190/3 "2019-08-27T00:14:13Z")

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When your knee is bent, some of the muscles are stretched. This triggers a reflexive muscle movment to straighten out the knee, to return the muscles to their ‘natural’ position. This means that while your knee is bent, you have a continous/repetati9ve isometric excercise. After a while, your muscles ache. Sitting still, with your knees unable to stretch, is unatural.

I’m not a physiotheripist. Don’t quote me.

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**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\
**Post date:** [August 27, 2019, 12:19am UTC](https://boards.straightdope.com/t/what-causes-bent-knees-to-ache/839190/4 "2019-08-27T00:19:16Z")

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How old are you? I can do that sitting in an easy chair.

Tris