Joint problems? No problem
All kinds of injuries can unable you from moving. But are you injured or are you simply sore? There is a big difference between both. It shouldn’t be an excuse though to sit on your butt and do nothing about it. Lower body injuries never hold anyone back from doing upper body training. OK, so let’s say you have trouble walking. Carrying weights could be an issue. A simple solution would be to minimize walking around the gym. One great workout, in this case, would be to use a simple method that would bring maximum results. For hypertrophy, I would go for German volume training which would pair up antagonist muscles for 10 sets. Grab two sets of dumbbells, one that you can do 10 reps of seated dumbbell curls with and another one that you can use for 10 reps of dumbbell lying extensions.
If you suffer from upper body issues, use the same principle for your legs. If you can’t hold a barbell across your back, machines could be your best ally. Hack squats, leg press, leg curls, step-ups, etc. Use your imagination, but at least, don’t let your injuries define your mental state. Do not become lazy because you’re hurt and leave all your gains behind. Just show up, work your way around it and with all the good hormones you’ll build from it, your recovery will come much faster than if you stayed on the couch.