New here- Marathon advice (after injury- plica)

Hi all,

I'm new here so hopefully posting in the right section etc. but I just wanted some advice...

I am now 22 but from the ages of 12-16 I had real problems with my knee (it was painful, locking, clicking etc.) I went to a physio weekly for 3 years and was diagnosed as having a plica (I used to do a lot of sports and running). Anyway after 3 years of regular treatment and another 4 years of monthly treatment including acupuncture, ultrasound etc. the symptoms dramatically improved. Since my knee healed I haven't been very motivated to exercise as every time I used to try it would flare up again. Over the past year the bit of exercise I have done (squash, gym, tennis) haven't flared it up so I feel like perhaps it's cured (although walking up a lot of stairs does still cause pain) My partner has just started training for the 2010 London marathon and I would really love to do it with him. I just was wondering what physio's opinions are on me doing a marathon after an injury like this.. could I cause long lasting damage? Is there anything I can do to protect my knee. Any advice would be really appreciated. Thanks, Gemma