For me it has been a 10 year long journey to get to where I am as a rider. So basically, trying not to bore you all, this is my story and hopefully it will help some people.
I used to race week in week out around UK, NPS's, Midlands etc. Then after a NPS at Ae forest I went to some local trails and stacked it in the middle of a set of trails. I was in alot of pain and couldnt walk or straighten my leg. I had hyper extended my leg causing a serious minicus tear and ACL rupture. Weirdly I didn't go to the doctors for a month as I thought it would get better but I was off work for 2 weeks and still couldn't walk on it properly. So off to Oswestry ortho and got it sorted fairly quickly. I basically had my cartilage trimed and then my ACL was reattached to my bone using a 3 inch screw.
Rehab went ok, found it very hard as I went from riding full on to nothing and wanted to get back straight away. Mentally I found this very hard as I was very focused on racing and training but I couldnt do what used to. I also lost my job, so it wasn't plain sailing. After about a year I felt strong enough to race again and I entered a race and did awful. My confidence was completely crushed and although I had built up the muscles in my leg I still didnt trust it at all. After another 2 poor results I decided to hang up my race pants (well it was lycra back then).
A couple of years when by and my fitness declined along with my leg strength, and then I decided to get back into riding my hardtail bike abit, again after a few weeks I ended up at some trails and what do you know I do exactly the same again (note to self - do not ride trails). That was it, I sold all my bikes and forgot about it, but I couldnt because my knee was serious bad now, I couldn't even do the simplest of things without it dislodging and clicking, fairly painfully. I tried going to the gym, swimming and other stuff the strengthen it but nothing worked.
Reluctantly I went back to the hospital and had an MRI, I had again damaged my cartilage again and they couldnt even see my ACL but obvsiously the screw was still there. So I was told that I had to have 2 ops to correct it, first one would be to sort the cartilage and then second one to reconstruct the ACL from my hamstring.
After I finally had that done over a 2 year period, I got through the physio well and then started to get on the static bike in the gym (boring as hell) and other low impact stuff. It took a long time before I felt like I was ready to ride again but I don't regret all the pain and work I have gone through. I would say that now my knee is 70-80% of what it was before the first injury and I doubt it will be any better.
I think the key things, it takes time to heal and it can be so fustrating. You knee will never be the same but if you work the muscles and build them up then a good level of function can be achieved. I think its hard to put a time limit on how long people take to recover because of the complexity of the knee joint. I would say to it as easy as possible until you feel confident to sit on your bike and not even worry about your knee, that way you know you wont be mentally thinking about it when you ride.
Don't use your brakes.......