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What happens when the knees lock ?

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Having been in marching bands for nearly half of my life, I would like to know exactly why it is that we don't lock our knees while standing at attention. I've seen people get nauseous, see spots, and even pass out from locking their knees and I was wondering, anatomically, why this occurs. If it is because of cutting off circulation, which specific vein/artery is being pinched?

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replied August 17th, 2007
Arthritis Answer A3190
The knee joints can lock if something get stuck between the 2 joint surfaces. The joint’s surfaces are normally very smooth and allow joint movements. They are covered with synovial cartilage. Various conditions (inflammations, degenerative processes and traumas) can damage the cartilage and make joint movements painful, restricted or even completely impossible. In the case of joint inflammation (arthritis) cartilage becomes damaged by inflammation. Then, the chronic inflammatory process creates connective tissue that makes “bridges” between the two surfaces and disables the movements.

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