Not being plagued with arthritic knees I have a limited view on what that means. Squats are essentially standing up from a seated position, only without a chair and with additional weight sitting on your shoulders. Start doing squats with a chair and no weight. Then add some weight and keep the chair as a stop so you don't inadvertently go too deep.

If arthritis is affecting your flexibility -- I don't have the flexibility I once had so when I'm doing squats and move to the seated position, I probably don't go low enough to be legal per competion rules; I don't care, I'm not competing. I take it down to where my knees don't hurt and call it good enough. Some of the younger guys do deep squats with weight and I have to shake my head thinking what their knees will be like in later years. Maybe they need to train for a deep squat but I don't know why.

Squats are full body but at a point there is too much risk and limited gain. There are a lot of muscles engaged and working together when you do a squat. You don't need to go all the way down to get the benefit.

Just my amateur opinion.

Thanks - very helpful.

If you don't have creaking knees, don't acquire them - not recommended.

One way to make squats safer is to use a Smith machine.

Machines can be safer but one of the benefits of free weights is it forces the balance aspect which means different muscle groups working together. Once you eliminate the problem of balance you move from a 3D exercise to a 1D exercise. Two of those dimensions may be near zero, but that's the point; you need to keep them near zero.

When I started doing bench presses again after having used various machines for years, the bar started wobbling -- left/right, toward my legs/head. Machines won't let the bar do that so it's a one dimensional exercise, strictly up/down. Safe, but you lose the finer muscle engagement. There's probably a happy middle and that would be to use both. Use the machine for power with safety and then use free-weights to train those "other" muscles.

I sorta do this, using a machine for leg presses and then free weights for squats. I do lots of weight on the machine, worst case I get stuck at the bottom and am forced to crawl out of the machine when it hits the hard stops. Then I'd start removing plates hoping nobody saw my faux pa fortunately this hasn't happened to me (yet), but I saw it happen a few years ago. Rather than the lifter crawling out we started pulling plates until he could press the remaining weight. No harm done.

Regardless, there is a trade-off when going to a machine.

Well said, absolutely right.

Try a leg press machine. You may find that if you use it 2 -3 times a week, and gradually increase the resistance, you will be able to move on to squatting.