Squats and bad knee(s)

Ive been talking to some lady friends of mine who want to lose weight and of course due to t-mag and this forum I always push free weight training as well as diet. As i get to mentioning squats Ive found out that a few of my friends have knee injuries either from accidents or sports. So should they even try squats to just parallel or just work the legs in other ways? Also, what other exercise could replace squats and provide less stress to the knees?

Try having them box squat. Tell them to sit back far enough so that their shins are past perpendicular to the floor. This reduces the stress on the knee. I know a girl who said she couldn’t squat because previous knee surgeries. I had her do this and now she can squat just fine. I’m sure there are people who can’t squat because of knee problems, but most of the people who say that are just scared to squat.