Thank you all, I am crying with laughter, i really did need cheering up.
Here's my slightly deceitful one.
When I was about 10 I was climbing up the walls of an alleyway, with one foot on each side, (as you see on TV), as I did this my mate thought it would be really funny to pull my foot away, I broke my wrist. I told my mum, I'd fallen off the kerb.
Fast forward a few years, I was in a roller skating hockey team, I was very good and very keen, unfortunately I fell one day and seriously injured my knee. I was in this huge elastic bandage from ankle to thigh and on crutches.
I'd had this for about 2 weeks and was very bored, so I went to watch my mates skating. Anyway thought I would get away with a quick whizz round , I didn't. First time round I fell over and broke my wrist (again). I knew mum was gonna be mad so I went to bed with a broken wrist and didn't tell her to the morning...oops