Yeah, casein is super gluey stuff, like gluten is. I had some pure casein once and it was incredibly hard to mix with anything because it was so gluey. And anything you used to clean the container... you had to throw it away it created such an uncleanable gluey mess!

Have you looked into arthritis diets? I know Dr. Fine thinks oxalates are potential problems. He likes the Paleo diet but thinks nightshades and oxalates are possible problems especially for arthritis.