Yes, Luxating Patella is pretty common. Did he say what Grade he felt they were? LP has Grade 1 to 4 (3 & 4 IMO are bad and should get surgery to stop further luxation).
Here are some tips.
NO more jumping. I have about 6 Foam Ramps around my house that I got from Ebay (search for Foam Ramp).
A lot of us are using a product: Cosiquin
Not sure about the rubbing of his knees though
