Here's an updated version of an answer I gave to a similar question a few years ago. Some of this does not apply to the OP, ditrina, who has already committed to surgery, but it may help others who are considering it:
I had both knees replaced (in one week

) in August, 2011 at the age of 67, and I couldn't be happier with the outcome. They'd gotten so bad, I could not stand for more than 30 seconds without significant pain. Standing at the firing line at a range was not possible. Now I routinely spend two hours on the line and don't even notice my knees. Cold weather does not affect them in any way. The only pain I have experienced since the surgery was a few brief moments of endurable pain that occurred during post-surgery physical therapy.
Here are some things I learned from the experience:
1. Don't wait too long. I went to a highly regarded orthopedic surgeon who checked out my knees and told me he couldn't do the surgery, because my knees were deteriorated beyond his ability to help. He referred me to a "surgeon of last resort", who specialized in severe cases. Mine were the severest of the severe, because he told me after the surgeries that my knees were the worst he had seen in at least 6 months. If I'd had them done earlier, it might have been easier for all concerned.
2. Find an orthopedic surgeon who has had formal joint replacement training beyond what is taught in an orthopedic surgery residency. My surgeon spent an additional year honing his joint replacement skills at the Anderson Orthopedic Research Institute in Washington DC.
3. DO YOUR PRE-SURGERY PHYSICAL THERAPY! (I'm shouting this because I think it is critical for a good outcome.) I don't know if there is any research on this, but I suspect that a lot of people who skip this live to regret it. The "knee replacement" is really only "cartilage replacement". The rest of the knee components, the ligaments, tendons, muscles, and kneecap, are not replaced. Because arthritis causes them to shrink, shrivel and lose elasticity, they'll hurt like hell when the new artificial knee is installed, unless they have been pre-stretched by physical therapy. I spent four hours a day over 2 weeks prior to surgery doing physical therapy, and I attribute at least part of my successful outcome to having done so.
4. Plan on a month or so where you're "out of service". Three or four days in the hospital per knee, and two to three weeks flat on your back at home during recovery. During that time you'll have regular visits by nurses and physical therapists, and you'll be up and about on walkers and canes while they're there, but much of the time you'll be in bed. It will probably be five to six weeks before you're cleared to drive again.
5. Keep ahead of the pain, both in the hospital and at home. If you feel pain coming on, take your pain meds before it gets too bad. If you get all macho about it and try to tough it out, the pain will increase your misery and slow your recovery. Once home, I kept a log of my pain med intake. I could take up to eight Norco tablets (a combination of hydrocodone and acetaminophen) a day at six hour intervals. By the fifth day at home, I was down to four tablets a day, and over the next ten days, I tapered down to one per day, and was completely off them after 20 days at home. I experienced no withdrawal symptoms, but had narcotic-induced constipation. Prepare to drink lots of prune juice.
6. Be nice to your spouse/significant other/family members, because you will be pretty much helpless and totally dependent on them during the early stages of your recovery. Mrs. swsig was a godsend, waiting on me hand and foot during that time. I attribute much of my quick and uneventful recovery to her efforts.
7. Do your post-surgery outpatient physical therapy. Ask your home visit therapist to recommend some good physical therapy centers to go to after you're discharged from home therapy, then go religiously. Yeah, it can hurt some times. But after all, you have to live in your body, so you might as well make it as good as it can be.
8. I had a post surgery sleep disorder for a couple of months, possibly due to having two surgeries. Fortunately, being retired, I could sleep whenever I wanted, so it wasn't a big deal for me.
9. I was pretty much back to normal activities six weeks after surgery, and was able to fly to San Diego for my 50-year high school reunion 2 1/2 months after surgery.
10. If you have the surgery, you'll be taller (the artificial knees add about an inch), thinner (the painkillers slow down your digestive system and kill your appetite), and better-looking (at least I was

).
Best wishes for a successful outcome!