Managing content means keeping things fresh and consistent. You should regularly remove out-dated content. When you review responses in the Knowledge Base, remember to look at the tags and the date the response was last used.
Some content can be updated, or refreshed, while some might just need to be deleted. You can select content in the Knowledge Base and delete a record individually.
Or, from the list view, you can also select a number of items and delete them in bulk. Use the control on the top left to do this (called Bulk Actions).