In a most undignified manner! Basically, balance on toes/knee [if possible] and hands, like a crab and push up. It's not pretty, but it works. Come up in stages.
I wouldn't try it for a while, but it you work PT hard and get a decent bend in your knee, it is possible. [PT/doctor say 120 degree bend is the goal; I have 136 degree bend in both knees and that really makes a big difference in mobility and stuff like getting off the floor!]