Not something I’m very knowledgeable about in general. I assume you mean a dislocation of the patella?
To him or in general? If it happens to him frequently, he might want to look into surgery but don’t take that as medical advice please.
Regarding your question: It’s not that easy as a patient to identify a good physio, depending on your own believes about the body, illness and pain etc. because you might be faced with approaches going against your own confirmation bias. A simple example: If you think vertebraes or your SI joint can misalign and you want your physio to realign them but he tells you that’s simply not possible, you’d probably think of him as a bad physio, even though he is objectively right. You know what I mean?
There is a lot more on that topic but I’m on my phone, so just a few pointers: A good physio will place emphasis on adequate education, use up to date models to explain pain and disfunction, will go for an active approach and only use passive treatments when they’re justified (which isn’t that often), he will concentrate on the cause of your issues and not only the symptoms, he will form a therapeutic alliance with the patient but won’t make them dependant of him and teach them to help themselves.