Dr. Mundo Runes explained
There's one set of runes for Dr. Mundo on patch 15.4 that is the clear favorite for LoL players and pros alike. The best Dr. Mundo rune paths on the position 
Top are 
Resolve as the primary path and 
Inspiration as the secondary path with a pick rate of 99%. Besides picking runes on Dr. Mundo you should learn how to play Dr. Mundo and if you are interested in pro matches take a look on how a pro builds Dr. Mundo. If you want to discuss 
Dr. Mundo then you should visit the champion subreddit.
Dr. Mundo runes from primary path
Resolve empowers the survivability of Dr. Mundo and increases the tankiness. Most of high elo players – and our LoL pros in the the major regions – have agreed that Grasp of the Undying is the best keystone rune to run on Dr. Mundo. This keystone rune gives Dr. Mundo alot of sustain and helps to force your opposing champion out of the lane. Other primary runes on Dr. Mundo are Demolish, Second Wind and Overgrowth.
Demolish increases your pressure on the enemy turrets. This rune will help you to punish bad roams or backtimings of your lane opponent. Second Wind powers up your sustainablity in lane by healing after taking damage from an enemy champion. Overgrowth increases your maximum amount of health.
Dr. Mundo runes from secondary path
When it comes to your secondary path, most Dr. Mundo players prefer to go with Inspiration. Inspiration opens creative opportunities on Dr. Mundo troughout the match. On the Inspiration path, the best runes for DrMundo are 
Magical Footwear and 
Biscuit Delivery.
Magical Footwear allows Dr. Mundo to focus on those essential core items without the need to spend the additional 300 gold on boots. Biscuit Delivery is a great rune for laning as it gives additional health and mana, which can help in more aggressive lanes.
FAQ for Dr. Mundo Runes
Which is the best keystone rune on Dr. Mundo?
The best keystone rune on Dr. Mundo is Grasp of the Undying. This Dr. Mundo runes setup is then referred as Dr. Mundo Grasp of the Undying.
What runes does Dr. Mundo use?
Runes from the paths Resolve and Inspiration are the most used runes on Dr. Mundo. For the exact pick rates of Dr. Mundo runes used, you have to study the rune distribution presented.