Badly bruised and scraped knees

Went over my ankle running downhill on tarmac and landed heavily on my knees 2 days ago, then had to walk over a mile back to work (I was running from work at lunchtime).  So i now have sprained ankle and two battered knees.  Left knee is worse, there is a small gash and scrapes at top of kneecap and then bits underneath (bits you would kneel on) are all scraped and were bleeding.  I've obviously banged the top of my knee then also scraped the rest of it. My whole knee seems to be bruised and a bit swollen.

How long should it take for this to calm down and before i should worry that i might have done some real damage to knee ? 

I can manage going up stairs fine and going down stairs not too bad either, i think main pain is really from the skin and scabs stretching when i bend my knee.  Obviously becasue its all swollen and bruised that isn't really making it easier to bend.  To top it all, i ruined my newest pair of running tights as well, big holes in both knees !!

Sympathies. It's likely to take several days to settle down noticably and longer than that (two weeks or more) to go away completely, based on my experience (I bashed one knee like this while I was away at a conference in the summer, three miles into a 20 mile run). In the first several days I found I had to make sure I could keep bending and straightening my leg - if I stayed with it in one position too long it stiffened up.

Bland antiseptic ointment or simple white aqueous cream dabbed on should keep the scabs moist so they don't harden then crack painfully every time you bend your knees...