Strange that they put you in a cast, I was told that was old school style and the braces were much better. I was braced from the start (mid May 1st surgery) and for about six weeks (end of June, coinciding with my first physio session). I only got it off that early due to following the consultant’s guidance with incredibly strict adherence. The risk I had was, due to the severity of the fracture (severely comminuted), if the brace came off too early then there was a good chance my quads, hamstrings and calf muscles would tear my knee cap to pieces again.
The bruising took months to go down on my knee and it extended half way to my foot. I recommend getting a reusable ice pack to help with the swelling, you can pick them up for about a fiver from any chemist. I got one that slides into a pouch that you can wrap around, which is pretty useful.