As I explore, learn and discuss this with folks, I realize, we know he has fluid build up; that suggests a ligament issue, but it is not definitive (could be something else). If it is a ligament, we don't know which one, and we don't know the extent of the damage. Starting to lean towards seeing the specialist, at least to learn more about what the issue IS. My vet said the specialist will likely start with an MRI. What didn't "click" with me is, THAT will be to id the issue more clearly.