Joint pain is obvious, yes. Cardio, not so much.
I won't go into it too much (he says, going into it too much) but I had a wakeup call on one of my first rides back after a year off with injury.
A two hour slightly hilly ride, nothing too extreme. Felt slightly winded and tight-chested but otherwise as good as you'd expect for one coming back from injury and significantly heavier than pre-injury.
None of the normal sensations telling me to back off. No lactic acid, burning muscles or gasping, except the usual sensations on steeper climbs. I put being winded and tight-chested down to being unfit and my clothes being too tight.
Looking at the numbers after the ride showed I was in Z5/Z6 for the entire 2 hours. My average HR was 181, max was 196. (For comparison, my pre-injury numbers were ~145 avg/160 max, if fresh, and lower if tired, and my theoretical max HR was 182).
Cardiac stress test in the hospital showed that my heart was ok, but that I was redlining very easily and pushing my heart far harder than I realised.
I now watch my HR like a hawk when out on the bike rather than relying on feel. (And I'm never taking health for granted again.)