If you have an injury that's not too serious, you can still get in some good training in the exercise room. Here's an example:
A couple of years ago, myright shoulder jointwas stiff and painful probably due to my football playing days in college.I decided to do weight lifts that didn't put too much pressure or pain on the joint.For example, the bench press really hurt myshoulder jointbut the chest press, shoulder press, cable chest press and triceps dips exercises didn't hurt that much. So, I used these exercises to work around my injury.
After about 6 months, the pain in my shoulder was gone and I don't have any problems with the shoulder joint.Because I worked around the injury with other exercises, they regenerated the soft tissues around the joint and the shoulder was rebuilt stronger.
Each injury situation is different but its worth trying to work around your injury to see if it will heal. Just a note: if you have acute pain in a joint, you need to see a doctor! Don't try to work around this type of pain!