This is an excellent overview on Joel Jamieson's site about how our body adapts to stress and when injuries occur, in general.
It's not specifically related to gymnastics or joints. Joel knows his stuff and has a lot of practical experience.
http://www.8weeksout.com/2011/10/05/the ... -injuries/
As an aside, professional athletes don't train full bore year around. But reccreational athletes
are more likely to. Make sure that you get adequate rest, nutrition and take breaks throughout
the year to have the best chance avoiding overtraining and injuries that won't heal, IMO!