Quad strength is important. Have you access to any kind of a stationary bike? I finally brought one for home from amazon. It takes awhile to make full rotation but eventually after warming up I can go all the way. I also have a medicine ball and I lay on my back, put heels on ball and draw legs to chest for as long as I decide, both good for quads and are possible with our limitations.
I was also told to always step down with bad leg and up with good leg, but you might have figured that through the pain if you do the opposite . Have you sought a revision doctor. Have you been told your issue is scar tissue.