

I have a site on medical information which has about 20-25 major topics. Let's say that the main topics are the following.
ankle
elbow
wrist
finger
knee
shoulder
neck
hip
toe
I need to do two things: (i) set up an area that shows these 2 dozen categories in one place, and (ii) have a landing page for each topic that will tell users where they can find resources on the site and will have latest entries in those areas (like rss feeds on the page.) So I've seen people do two things:
1) MENU: I've seen that sites will either have a dropdown menu with all the topics if there aren't more than about 15-20 or so. Alternatively, they may have links to all the topics in the footer at the bottom of the page.
2) LANDING PAGES: So where should these topic landing pages be where it says we have a forum, articles, etc. and some rss feeds on that topic? I have seen people put these landing pages in a subdomain since they might be thin. Some put it on the subdirectory but I don't know if that's a great idea especially with the thin pages. I wonder if I am better off putting content also on the subdomain or directory because I see Google giving a lot of weight on each subdomain as if it is a separate site when it really isn't.
Would be great to know your opinions.
So I want to have a dropdown in my main top navigation called "topics" which has a link to each page. These pages won't change a whole lot except for some RSS feeds on them. I notice many people are putting these landing pages as subdomains but the content is also on the subdomain. Problem is that if they are on subdomains, I lose the value of the domain having all the content. So since there isn't so much content on these pages I figure I should have the menu go to subdomain.site.com like knee.jointsite.com . So here is a summary:
(1) Do I have any danger in putting about 25 topic links in my main navigation bar on top of the page? That would be 25 links to load. Should I put those topic pages in the footer? If in the header, should they be "no-follow" links?
(2) Should I put these pages into the subdomain or the subdirectory in order to minimize penalties from google or panda for "thin" content?
Thanks everyone for your thoughts.