Hi Becka

There are different types of bone cysts so the Ortho should inform you what type:

Unicameral simple) bone cysts
anneurysmal bone cysts
traumatic bone cysts

Did he/she say what type it was? If it is a simple bone cyst have a look at this site:

Your Orthopaedic Connection: Unicameral (Simple) Bone Cyst

So this type of cyst has nothing to do with cancer, is benign but doesn't seem to be very well understood (eg why they occur)

Why the non weight bearing? The ortho maybe concerned enough about the cyst, potentially collapsing, hence why the non weight bearing (although I don't know that). However I think it would pay to go and find out from the ortho exactly what the thinking is. To have you off your leg is a major issue and as you are worried I think it would pay you to go back with a list of questions you want answering. For example:

What exactly have you got ie is it a unicameral bone cyst.
As it is causing pain is there a risk of it collapsing causing a pathological fracture
How sure is that it couldn't be something else - should it be biopsied?
What is the rest supposed to do? How long will this go on and when will you know that it has worked?
why not surgery at this stage. If surgery is warranted what would it involve?

You are entitled to know more.

I'll have a look on a database at work if there is any more detailed info if you like.

In the mean time keeping fit would be good! your PT should be able to help you with this - aqua for example.