Some studies I have read suggest that Lyme disease symptoms can mirror those of hip dysplasia. Since you have had your dog's hips evaluated, it could be reasonable to conclude that it does not have Lyme disease. That being said, if you are concerned about Lyme and your dog has been in areas prone to ticks, and/or you've found ticks on your dog, it would be a good idea to have your dog tested for it.
Regarding the hip dysplasia diagnosis, it is heartbreaking but not the end of the world. Your dog can still lead an active life, in moderation and can be kept comfortable. I too have a dog with moderate dysplasia; I keep his weight down, walk him regularly for exercise and keep his mind busy learning skills that his body can do.
