I've just been reading what Doe has been saying to Jwells84. So, I'm still here. lol.
Jake does have his balance issues, and his differences with his left and right sides. Which are constantly being worked on. With his age I wouldn't be surprised if he has the beginnings of arthritis. As time goes on, he gets longer and slower warm ups. As for other pain, it is possible but my vet has shown no concern, only advising me that he may need the longer warm-ups.
Doe, out of curiosity what side do you see the most stiffness and unbalance on? Jake is toed out on his left front, which may cause a difference in how he moves and muscle structure. It has very very slightly progressed as he has aged. I leave it shod true to how he is.
Also what exercises do you propose to build on his balance and symmetry?
Natasha - It looks similar, but the owners of that horse said the horse did that consistently, whether saddled or not. While Jake only does it after being cinched up. They could be related incidents though.
It's a bit like the chicken and the egg, which came first when neither exists without the other. His toeing out makes perfect sense and will be largely the result of his problems rather than the cause of them.
95% of lameness is related to the foot, but in turn the foot is a reflection of the body. Hence why one must trim to the internal hoof capsule balance and not to an external angle or picture.
His leverage line is very unusual and interesting. I must find a way to draw it. However it is thrown off to the left but actually naturally falls to his right, and the reason it is thrown is because it actually directs upwards not downwards. This cause a kind of twisting.
So stiffness - this translates to his left side along the ribcage, we here he will seem to flex more easily but in actual fact is usually more bent that way and so as a bend it's actually bending less which confuses people. It will also show a vertical stiffness in his right hind which translates to a difficulty in transitions, especially to canter. I would expect him to fall out on his left shoulder (right turns) and fall in on his right (left turns). I would also suspect he has been susceptible to undiagnosed stomach ulcers and may still have a propensity. (hence also colic in rich grass situations for example)
In terms of exercises, there are many. I am trying to pull some resources together at the moment as it would take pages of typing and needs illustration. However I would highly recommend Peggy Cummings for Jake if you fancy buying a book. That's the basic type of work he needs.
I am so happy he has an understanding owner. Incidentally shoeing to how he is I would agree with as per above. Trying to change it with shoeing would just add additional stresses.