I would just like to add that although machines have their place and are great at helping beginners learn certain movements and build up strength, I would advise against using them longterm.

The reason for this is because many machines have a set path and range of motion. Because not everyone's body is made the same, this can cause problems down the line since the movements are not natural. You are also recruiting less of the smaller muscles in your body that help with stability and balance, while only developing the larger/dominant muscles. I believe that to truly be strong you must train all your muscles to work effectively as one system.

Ironically, some of these types of issues can be exacerbated by machines. They often limit you to a fixed range of motion which doesn't line up with your anatomically natural range of motion.

Obviously limitations from injuries are extremely specific to the individual, so your issues may legitimately cause some barbell lifts (particularly bench presses) to be a bad idea. But I do also personally know of a lot of anecdotal evidence that points to freeweight exercise reducing the impact of people's injuries: e.g., knee pain from squats in a smith machine disappearing when performed in a power rack.

Understandable. Without knowing the details of your issue, all I can say is that even light lifting with free weights will help develop your secondary/stabilizer muscles. You may or may not be able to make it a mainstay of your exercise program, but light to medium free weight exercise will improve your joint condition over time as well. If you do anything that feels iffy, just be sure to get a spotter. Pretty much anything you do in a gym will make you stronger, except getting injured.

I second this -- if lifting heavy things makes you nervous, try lifting lighter things. There's a lot of small stabilizer muscles in your body that will be really weak if left unused, and lifting any free weight will help build them up.