1. Pain meds. Three weeks is still painful for most of us and many take strong pain-killers for several weeks. However, if you can manage with Tylenol (2 x 500mg four times a day = 4000 mg., the maximum daily dose), you can wean off the Percocet. With Tylenol be careful to count ALL the acetaminophen (active ingredient in Tylenol) in all the meds you take. Percocet itself, as well as many cold remedies, contain acetaminophen.
At four weeks post-surgery, I found Tylenol surprisingly effective!
2. Getting around the house. Almost like a BTKR, you say... well I am one and at three to four weeks I was... barely getting around the house.

The knees hurt! They were stiff. They were difficult. I was still using a walker and had only begun to try walking outside on my driveway for a very short distance. I’m sorry to hear your 2013 TKR is still giving you problems this significant, but your 2018 TKR is doing pretty much as expected in this department. Three weeks is very early in recovery. Your knee is inflamed and angry and has lots of healing still to do.
3. Wedding tomorrow. This is a challenge (as you already know). If you can stay home, might be best. But if you go, prepare. Like Jockette said: Arrive late and leave early.
Minimize walking. Don’t be brave and walk across any parking lots. Be dropped off at the door. Bring your walker (not just a cane) to have the most stable walking aid available. If you don’t want a walker, absolutely minimize standing. Bring your cane also. You will need it for steps.
Keep in mind that bathrooms might be a challenge.
Sit at every possible opportunity, meaning all the time if possible, and arrange some way to elevate your leg(s). To this end put a couple of firm pillows in your car trunk and use them if needed. Put pretty covers on them if concerned about appearances. Elevating your leg(s) is a must. A large ice chest makes an excellent ottoman (see next).
Ice as much as possible. An ice chest in the trunk of your car and a supply of ice packs (or bags of frozen veggies) would be good. If there’s a freezer at the reception, you might arrange to stash your packs on site. An army of minions (or a spouse or helpful young family members) to fetch them can be arranged. You will be very happy you brought ice.
If you have a pretty throw, bring it. Icing can make you feel cold and you will be happy to have it.
If you have a long drive (not good at this point either), support your knee and ice it during travel.
Don’t worry about what anyone thinks. You are setting a good example for others.
