You seem young to have arthritis, no?
Anyway, if you have knee issues you definitely need to be careful not to aggravate it because you won’t get far with lifting and will have other issues in life. Squatting once a week and making slow progress is better than messing up your knees more.
Yes I feel I am too old to have arthritis and thought it was something more which is why I’m pursuing a second opinion. Some days it goes well but some days I skip squats or modify as needed. I know because of my knee I haven’t pushed hard and taken it light which is partly why my numbers on the squat are low.
You could post a video of your squat so we can see what’s going on, if your knee are caving in or something like that it could explain it. You could also consult a physiotherapist or sports doctor.
I’d keep it flexible man. Hit the basics each time and try to add a little more weight or reps when you can. High frequency with low volume is the magic bullet for a lot of people. If I had to do my training in three days, I’d do something like this:
Bench 1-3 sets 1-8 reps
Squat or DL 1-3 sets 1-8 reps
Rows, pull-ups, and other accessories