Hi Elise,
sounds familiar - Ive had a pin in for 18 years for similiar issues - biggest difference is that there was no bone deformity.
The pin at the top of the tibia is holding down the patellar tendon - they probably moved yours slightly to try and improve stability (thats what they did to me too).
I was tender over the pin for years, and then I started to build bone over it - theres a nice definable 'lump' that is clearly visible on my leg, and if you press it its bony. Ive seen my most recent X-Rays and you can see where the bone has built up over/around the pin.
My physio says that over the years Ive 'pulled' at the patellar tendon and that bony build up is a result of this pulling, no harm done, just means ive an extra bit of boniness over the pin. Its also an attempt on my bodies part to 'smooth over' a bone protrusion i guess.
In a case like yours where the pin is causing problems they can remove them - it means that the work done to pin in the patellar tendon no longer requires the pin to hold it in - the tendon now knows where its supposed to be if you know what i mean

I think its unlikely that swelling can loosen the pin after 9 years - however if you have had traumatic dislocations i suppose its possible that the tendon itself has been pulling on it?
If you are concerned that you may have an infection i think you should go to your GP and voice your concerns, its your body and if you have been feverish on and off for 10 days then perhaps its time to see the doc. Explain your fears that you wonder could the pin be a source of infection - your doctor should be able to tell if that is happening.
Are you seeing your OS again before surgery? what is the surgery for? they are going to remove the pin - are they also going to try and stabilise your knee?
best of luck.
tanya