My startup is actually working on this exact problem: https://tettra.co
Our philosophy is that knowledge should be fast to capture, accessible from your communication tools (Slack, etc) and open by default for everyone on your team to suggest edits because most knowledge goes stale in other systems.
Would love feedback from the HN community. We're documentation geeks here and love talking about this stuff.
If you're interested in using the product, we can offer a special HN discount of 20% off the first three months. Just shoot us a message in the chat. I'm on there right now.