Well, actually, Bella, it will disappear in stages. The worst should be gone in anything between a few weeks to a few months. Even then you may find that it comes and goes, like one day you'll wake and find it significantly reduced but later in the day it will come back. Another time it will be gone for a whole day and then back the next day. It's kind of unpredictable.
A lot of the swelling, particularly in the early weeks, is due to the use of the tourniquet during sugery and therefore is to be expected. Some people find that in this period the swelling is extreme and prevents them getting good flexion but it passes eventually. People also sometimes think they 'should' be off pain meds about now and try to tough it out regardless. But remember that pain can cause swelling as much as swelling causes pain. One of those nice little vicious circles life visits upon us from time to time. But it's a simple rule - to reduce the swelling, keep taking the pills!
But the residual swelling, in one degree or another, will hang around for anything up to a year. Just stick with the mantra ... elevate, ice, rest and pain control.