The search is designed to return the most relevant results first, regardless of date. It's definitely a feature we're looking at, though I can't make any promises about if or when anything will change.
An alternate way to search sitewide is to use Google - while Google doesn't return results in date order either, you get bigger "snippets" of the posts in the results so you can rule in/out what you were looking for. You can even narrow to specific forums.
Forgive me if I'm posting info that you already know, but to do that, you go to google.com.
type in the search word(s) you're looking for, followed by site:
medhelp.org
If you have more than one word and want only results in that specific order, put them in quotes, e.g.:
"tendon injury" site:
medhelp.org
If you further wanted to narrow results to just the orthopedics community, you can do that by using the URL of the specific community:
"tendon injury" site:
medhelp.org/forums/Orthopedics/show/60
If the words aren't necessarily going to be in order, don't put them in quotes or you won't get results:
tendon torn hand site:
medhelp.org/forums/Orthopedics/show/60
just make sure to remove the http:// and www from the URL. Hope that helps!