DD16 noted that Russell was pretty much dancing on one foot there at the end. I think he genuinely did hurt his foot, probably when he jumped off the stage during that three-guy hip hop performance.I think he was distraught because he knew he had 2-3 other performances coming up in the show and he just couldn't do them. At the end when he was talking with Cat Deeley I think he was just so pumped he didn't feel the pain. Or perhaps they gave him a shot of Marcaine backstage to deaden the pain(Remember the winter Olympics when Nancy Kerigan had to perform a few weeks after the shin-bashing? That's how she did it, they shot her shin up with some kind of lidocaine or Marcaine.)
I broke my ankle running through the woods a few years ago. I didn't realize it was broken so I just kept walking on it for 6 days. It hurt like...well, you know. But it didn't keep me from doing all the shopping, cooking, playing with the kids and going to work. Don't know that I could have danced on it, and I walked with a limp but if I just gritted my teeth I could make it. So maybe that's what Russell was doing.
At any rate, I thought Russell was the best developed and most improved dancer. He was truly a beauty to watch. Russell has a long, illustrious career ahead of him.