I have actually suffered from Chondromalacia Patella or “Runners Knee” for 25 years, and at one time even ran a niche website / blog on knee pain that took me a few hours to put together, and pulled in a few dollars a day.
Google today have launched Google Health that is supposedly for US use, but I was able to log straight in, and add the ailment I suffer from. I am not worried about the privacy aspects.
The information provided is pretty basic as you would probably expect in a country famous for medical lawsuits.
One useful aspect of Google Health did catch my eye.
So if I was to recreate a niche site related to Chondromalacia Patella, those would be reasonable top level pages to build topic silos from, or sister sites such as back pain.
It goes without saying that Google have reliable information on this, and those keyword serches in the sidebar are about to get more traffic.
A.D.A.M. creates health content for consumers that is physician-reviewed by experts in their field.
Being the top related search terms, they would also be some of the best terms to use for Adwords landing pages, if they are allowed in your geographical area.