Great post! And, you are so right about recommending people with metal on metal prosthetics to get blood tests done to check their metal levels. Although I don't dance, I do improv comedy and teach it. I had a Birmingham Hip Replacement in 2008, and it started to make grinding and whistling sounds last year. I went to my doctor, and although the x-ray showed it to be in place, he ordered blood tests. Sure enough, I had extremely high levels of cobalt and chromium in my blood, and had to go in and get another hip replacement - only 8 years later. But, I am just lucky they caught it. If you have metal on metal - get your blood checked - and then keep dancing.