My wife have really bad knees. She really have a great body, legs and but, but need to maintain it with workout, and that is hard with bad knees. Can someone make a couple of moderate workouts for girls like her? Or give some advices at least?
Also message the sides or easier get a foam roller message all around the knees not on the knee since it's body pressure using a foam roller.
Water activities can take the stress off of the joints, if you have access to a pool.
Otherwise have her try leg exercise with light weights but watch the form. When squatting or lunging don't let the knees go beyond the toes. Try closed chain exercises(foot on a surface-ground or platform) and open chained(foot free-leg extension). Depending on what issues there are in the knee one form maybe better than the other.
And finally don't forget about hip and ankle stability exercises as well, they could lead to knee pain if the knee is compensating for hip or ankle instability
You should avoid leg extensions and leg curls altogether. They are notorious for wrecking knees. The landmine reverse lunge and defecit deadlifts seem like a good fit here. Hope this helps.