Chicken with a bad foot/leg!?

Hello all,

Hope you can give me some advice on one of my chickens who has developed a limp and isn't putting much pressure on her one foot.  It started on Saturday, when I saw my partner in the garden looking at one of the chickens and he was holding her up looking at her feet.  When I went out, he said that he thought she was limping but could see no sign of any swelling or any thorns or cuts to the pads.  He put her down and she didn't limp for a while then...!  I didn't actually see her limp until the following day, but since then it has got much worse and she is keeping her tail down when she does move around. 

She's still eating well, and drinking a lot it's just the moving around that is causing her some discomfort.  The foot does look slightly swollen compared to the other foot but we can not see any sign of cuts etc, and can not think of how she might of hurt herself. 

She's about 20 weeks old and an Amber Star (currently being called Amber - original huh?) and we have three other chickens (Rhode Rock, White Star and Light Sussex) who are all fine and dandy). 

If anyone could offer any advice as to what they think it might be or what i can do to help her please let me know.  thank you for reading 

Yes, I've checked her feet a couple of times and there doesn't appear to be any difference between her good one and her bad one.  She does perch at night also, which is about a foot high.

i've got the same probelm shes very slowly getting better , the slightest knock or anyhting can make them lame .

Just been out to her, and have found that both feet are warm to the touch, however it is rather warm around her ankle kind of area.  Would this suggest that she's just landed badly, and maybe jumping up and down off the roosting pole isn't helping with the healing process? 

No... it was an actual "*" placed as an action/some thing I was just about to do... I quote " *is running out to check on her chook's foot now* "

If it was a bleeped word, I'm not sure what it would of been... seeing as there is a star at the begining and end...

Any way... the chook's foot is still no better.