Across HealthUnlocked, communities can pin posts to make them easy to find. (Only admins can pin or unpin posts.)
However, many members fail to notice that they exist!
On a computer you can expect to see Pinned Posts at the top right of your screen when viewing a single post or a bit further down on the right when viewing all posts.
On a phone you can expect to see Pinned Posts by scrolling down your screen.
On both, you can see See all > in blue. Click on this and you will see many more pinned posts.