Knob and Tube Wiring with AFCI
I maintain 100 year old electrical systems. 

Knob &amp; tube is legit. Notice that most of the people telling you it's bad are people who stand to profit from your worry.  

Cities and the NFPA are not nearly as worried.

AFCI is a superb way to protect any wiring you're worried about.  I recommend it for aluminum wiring, backstab connections, you name it.  It will prevent arcing/sparking of the sort which makes connections hot and starts fires, not that K&amp;T has a problem with that. Like most electrical work of that age, K&amp;T splices are wildly overbuilt by modern standards: wrapped, soldered and insulated often with two kinds of tape. We use backstabs. 

People of that age didn't have our tech, but they were serious about their craft. Nobody had to tell them not to eat Tide pods.

Add GFCI protection to stop even small current leakage from wet wires,  and you are safe as can be. You can even put 3-prong sockets on those receptacles. 

One more thing. There was a concern that blown-in insulation packing around knob and tube wire would cause it to overheat. However, the states of Oregon and Washington did an extensive survey on this, and found it to be false. As such, they liberalized their laws to permit blown insulation around knob and tube.