Sheilagh,
I am so happy that Coffee does not need surgery. It's so strange that some type of repetitive movement he is doing at home has caused this. Does he jump off surfaces such as a sofa or chair? What about steps in the house or garden - are some higher than others? I have had one horrible thought, but I feel I have to mention it. Could this G_D forbid be caused by anyone working in your household? Or, when he is being brushed, if it is daily, is he held in a position that could be stressful to his body? Or, is he sleeping in a bed that causes him to curl his body the wrong way? There are just so many alternatives to think of.
I am still pleased for you though, that he does not have Hip Dysplasia. As for the groomers...... time for another parlor perhaps?
Big hugs,
Lauren