hello, I bought a horse back in august & was told he was perfectly sound & had no issues. I rode him before I decided to buy him & looked him over, everything looked & felt good. Beginning of September I had my farrier take his shoes off ( was planning to keep them off until spring time next year) but I started noticing that he was tripping a little more & figured it was just from getting use to not having shoes on. Well here & there I would notice a slight limp when he would trot. I'd give him a few days rest & he would be fine. Well about two weeks ago I entered in a gymkhana & that night when I brought him in for the night he was limp more then he ever had. I figured he might have stepped on something in his paddock. Gave him a few days & he was still limping. I have a friend look at his hooves & discovered he had a stone bruise. Cleaned it out & gave him a few days rest. The other day I put him back outside & he was walking & trotting around the arena great, well that night when I went to bring him in, again he was limping. I had him looked over last night & got told that he has a old tendon injury ( had to of happened when he was racing on the track) my question is will this keep us back for figuring anything with barrel racing. 

Horses come back from tendon injuries and run barrels, but it sounds like that is not healed if that's what's causing the limping. I think you might have to get it ultrasounded to find out exactly what's going on. 

 I would highly suggest a post purchase vet exam as it sounds like there was no pre-purchase exam (which may have uncovered this issue...or not depending upon how in depth).  Wondering if there was any special shoeing prior to removing shoes.  If so maybe there was a reason.

A vet appointment seems to be in order.