After your operation, once you are back on the ward, the physiotherapist will teach you how to use crutches and ensure you are walking safely. You will generally be able to put as much weight through the ankle as is comfortable. You will be informed if your instructions differ from this as may be the case with certain conditions, or if the arthroscopy is done alongside another procedure.
Realistically, you can begin to build up your activity from two weeks after your operation, but it will probably take at least four weeks before more vigorous sporting activity will be possible.