Horse Development

Question
I have a 3 year old quarter horse mare, I broke her when she was two and a half although I mostly just did walk/trot work with her. I have recently started working her at the canter and she is coming along great. She seems to have an aptitude for jumping (she jumped out my 4 foot pasture) so I was going to take her in that direction. Is it going to hurt her in the long run if I start jumping her lightly (once a week) now? I know her knee joint is closed, but I also  know that some other joints don't close until 5.

Answer
Dear Katie,
I could go on and on about justifying my response to your question but I think that your own gut instinct (demonstrated by the fact that you are asking the question in the first place) is that yes- you most definitely run the risk of doing this horse long term damage if you begin her over fences at three. If you want to get her conditioned to some pre-jumping gymnastic ground work- use ground poles. All signs point to WAIT. Just because other people do it doesn't mean that they should.
Best wishes,
S. Evans