What is the total number of knee replacements in the US annually? Hip
Replacements? Shoulder repalcements? Ankle replacements? What are
their average costs? What are the projections of numbers and costs for
the next several years? Are there other economic issues that are
associated with these replacements.

I am looking for readily available, valid, verifiable and quotable
sources for this information. The more detailed information the
better. You could email me links to studies and news that quotes reliable sources.