Jockette, it would be difficult to say for sure that any pain is the result of a metal allergy without doing the test. The problem is that so many things can cause the type of pain you're experiencing. That's why it's sometimes a good idea to get an allergy test if a person has had pain pretty steadily since their surgery. It's an effort to rule out one option without having to do anything invasive.
In your case, though, I'm inclined to think the problem is just that the partial was not a good choice for your knee problems. You cannot really make a correlation between an allergic reaction to jewelry and one that might occur with an implant. People who have had no problems with jewelry can have reactions that show up in the blood test. It's a lot of money out of pocket, though, and each person must decide for themselves whether it's worth it or not to be able to rule metal allergies out as a potential problem.
When you're ready to start talking with revision surgeons, this is something you should bring up as a question.