why do parts of your body swell up if you hit them hard on something?

Question

i was wondering because my knee swelled up like three times bigger when i hurt it.

Answer 1

Well, as far as I understand, if a part of your body experiences blunt force trauma, you break some blood vessels underneath your skin and the blood spreads all over the area, that's why it turns black and blue, it's due to the blood trapped under the skin. This process can also be your body's way of damage control, by surrounding the broken tissues with blood, oxygen is concentrated in the area and the repairs to the damaged cell tissues are facilitated, plus the swelling also temporarily immobilizes that area to prevent you from further aggravating the injury. The usual remedy is to put an ice pack on the affected area, to reduce blood flow and bring the swelling down.

Answer 2

Due to physical impact,the small blood vessels on the impact area been rupture and the blood leaking out and stay on around area also irritate the vessels; dilatation;inflammation.The result will be swelling redness,tenderness and back and Bruce.

Answer 3

I think its because all the blood rushes to that part of your body.