Discovered the answer. Although the documentation on the Vote object only mentions recording votes for Ideas and Replies, this data model diagram shows that Votes can apply to Articles as well. Trying to query for all Votes returns an interesting error message; apparently you can only query votes with certain filtering applied. I have confirmed, however, that I can create votes, at least for the current user. The voting user is recorded by the CreatedById, so it doesn't look like you can record votes for other users (which is fine for my purposes).
Agents can now search for articles, view the article detail page, and then attach the article to the case directly from the detail page, rather than having to go back to the article list.'
In the past, an agent could only attach an article to a case from the Article Search Results list. However, they most often have to drill into the detail page of the article to determine if it is the right article to attach. If they have to go back to the list, it may be frustrating to determine which article in the list is the one they were just viewing.
When searching for an article from a case, not in the Service Console, an agent can click Attach to case or Attach and Return to case.
Buttons to attach an article on the detail page
After the agent clicks Attach to case or Attach and Return to case, they become Detach from case and Detach and Return to case.
When in Service Console, there is only Attach to case. Attach and Return to case is not needed, as you can just go to the case tab in the Service Console.
Button to attach an article on the detail page in Console
You can also detach the article once it is attached in the Service Console.
If the agent initiates the article search from a case, they can attach and detach the article from the article detail view.
Note
These options are not available unless the agent is coming from a case article search. For example, agents must start from a specific case that they need to attach or detach an article.
See Also:
IdeaExchange: Return 'Attach' and 'Attach and Return To Case' buttons to full view of an Article
IdeaExchange: Knowledgebase: improve attach article to case interface
http://docs.releasenotes.salesforce.com/en-us/summer15/release-notes/rn_knowledge_attach_article.htm
Best Answer
I just tried this in a Trailhead org. You will need to put the Cases object in the Related List on the Lightning Knowledge Detail Page Layout for each of your record types. Once you do that and also have the Related Cases Component on your Lightning Page Layouts, Cases which have Knowledge Articles of that record type will show up on an article's Case Related List. There's no need for a junction object. It's just a matter of completing your standard configuration steps so that everything that's needed is there.