Hi Sally, sorry to hear about your issues. Often with an acute trauma it is difficult to ascertain what's truly underlying when that something is small and not displaced (e.g. a small fracture). It can show what are called false positives. In case they do suspect a fracture they have advised you to non weightbear and if in fact you have torn your ACL I would have you in a brace to ensure you don't. 3 weeks is a long time though now not to have a diagnosis so I would be pushing the hospital involved (I expect it is NHS) and jump up and down a little about it.
If you have no fracture the ACL will need to be reconstructed in due course if you want to do sports. If not you can discuss the options later. In my opinion I would always have a recon. no matter what I was doing with my daily life, and at 35 you've got a long way to go. My current advice would be to get the fracture diagnosis confirmed or ruled out. If you have one this can mean anything from a brace to a cast for 6 to 8 weeks and then some rehab to get the leg going following. If it is just ACL then the swelling itself is going to take quite some time to reduce and it will be uncomfortable until it does. If the ACL is gone then there could also be meniscal damage which may or may not be restricting the full straightening and some bending of the knee (the swelling will reduce flexion of the knee in anycase). Such a blockage can also be the cause of persistent knee pain at this stage.
The NHS should be providing an ortho clinic with referral to the Physio's to assist with the acute ACL & possible other ligamentous issues. Unfortunately without a physical assessment of the knee it is hard to provide specific advice. They need to work with you to identify which stucutures are causing you the discomfort and then assist with treatment options for that.
If you find you are not getting very far in the next week I would suggest booking just an assessment with a good sports physio in your area to do a physical assessment and provide some initial advice. You could do this now even to give you more of an insight and hopefully some treatment and ideas to help reduce the swelling and discomfort.
Sorry I can provide even more advice at this stage but let us know how you get on and we can see if we can then provide more input.
regards :-)