Hi. Welcome to my world. : )
My 20 year old QH is by definition a conformational trainwreck. He has weak pasterns and because of this, bowed both of his front tendons two years ago. That wasn't helped by the fact that we have to keep his heel somewhat elevated to help manage his mild navicular, and oh yea don't forget roll the toe because last fall he was diagnosed with severe high ringbone in his right front leg.
Here's the annoying part: the f*%@#$g horse is sound. Except for not being able to turn a very tight circle (he justs pivots on his back legs instead), and the fact that his legs look weird because of his angles, you'd never know there was anything wrong with him. When he was diagnosed with navicular, he was very off at first. The vet came out, x rayed him, we lifted his heels and put him in bar shoes and he was good to go. This horse was my barrel racing champion for the next 3 years. We also team penned, trail rode, the works.
When he bowed his tendons, he was never off, not once. Both of his legs were swollen and stocked up, but he still ran around like an idiot. The vet said two weeks stall rest, then give him three months off. No hard work, turn him out in a small paddock. Well, I didn't have access to any of that so he was in a large paddock 24/7 where he'd race around like Seabiscuit all. day. long. I swear I developed an ulcer worrying he'd never be rideable again. I compensated by giving him 6 months off and massaging liniment gel on his tendons everyday. I also put him on Smartflex Repair for a few months, which I think is a miracle supplement. Now, he still has the hard lumps of scar tissue but that's it. I have the opposite problem as you, when Chance doesn't work for more than a few weeks he gets stocked up. After I ride him his legs are totally smooth. The only thing I do now is use SMB's when I ride and liniment, liniment, and liniment after work.
So, sorry for the ramble but long story short: yes, they can bow a tendon and not be lame! I'm starting to think people put too much thought into trying to fix their horses. Best thing that worked for me was turn him out to pasture and massaging liniment. The vet thinks the massaging helped stimulate the blood flow to the area, therefore speeding the healing process. I don't care why it works, I just know it did. Anyway, good luck, and try not to rip your hair out!
I've spent most of my life riding horses. The rest I've just wasted.