Fortunately, I do aerobic Heavyhands (and have since the 1980's), so I get a good aerobic workout even with just upper body work. Before the knee osteo, I used to have a small step machine, and I would do that simultaneously with HH. GREAT aerobic workout. Unfortunately, when the knee went, the stepper also did. Just couldn't use it.
The main reason that people talk about how people should do low impact activities is that the joints wear out over time. People become immobile. lack of exercise kills them.
sounds like you dodged that bullet.