Actually, that horse was very rideable. He is now retired at 20, but he was shown all over, and was eighth in a class of 20 at the World Championships some years ago.
His saddle was pretty much custom to him. He was never lame, never sore, never put a foot out of place. He has no difficulty moving, running, rollng, kicking, trotting, carrying weight(granted we would never ask him to carry a very large rider), he could drive with the best of them. He was actually the horse I learned to drive. He could and did everything a straight backed horse could do with no trouble at all.
That is the interesting thing about lordosis. Horses are about the only animal that can have such an extensive spinal condition without messing with the nervous system or other functions. They are pretty much "normal". The back does not affect their performance any. I could go get him and ride him tomorrow. We still have his saddle. I don't think his back would be the thing that would give me trouble, but his "I'm retired, let me back out." attitude.
Here he is and one of his pasturemates who is a lesson horse. The chestnut is probably 19(I'll have to check), and is about to come out of retirement to teach little W/T lessons. These were my sister's early horses(my first horse is actually the sire of the chestnut and out in that field as well). The bay is actually an orphan and to this day sees my older sister as Mama. They are family. Even though they are capable of doing, and we just don't use them, they earned their place a long time ago.
The chestnut's back was an interesting story, that makes us believe something different than the usual Why? to lordosis.