How does Lionel Messi manage to remain relatively injury-free even though he's knocked around so much every match?

Pep Guardiola's arrival at Barca in 2008 had a large part to play in Messi remaining relatively injury free. This article throws some light on that... http://www.goal.com/en-india/news/2292/editorials/2012/10/23/3469793/how-messi-went-from-injury-prone-teenager-to-bionic-man

Agree with the points made by Aaron and Parag. The great balance also helps him to avoid the bad tackles, the ones which damage ankles. Remember the tackle by Aldo Duscher which had knocked out David Beckham. Messi would have jumped over or around it. That combined with the falling better helps him avoid the bad injuries. Guess that helps most of the shorter, more skillful players. In addition to being dexterous with the ball, they are also nimble around falling legs.

I would also like to add a point in addition to valid points raised above. Messi has played in La Liga for his entire career. La Liga is bit soft and less physical. It would have been different if he played in Premier League. Also, he would definitely have not scored so many goals in Premier League.

This is an excellent questionMessi is not a physical beast like Ronaldo or Ibrahimovich who could sustain the horrid tackles of the defenders. He is thin, agile and very fast. A fast defender could knock him out easily. He also cannot out muscle the defenders. Messi stays injury free because of his ability to avoid tackles onto him. He positions himself in such a way as that the defenders cannot evade tackles onto him. He has immense footballing intelligence. The other reason he stays injury free is his short height. His height which is about 170 cm gives him the ability and agility to avoid the defenders. Messi’s play style is not flamboyant like Ronaldinho or Neymar neither purely based on technique like Zidane or Del Piero. He runs ruthlessly and is aggressive towards the defenders. His short height combined with a rather aggressive style of taking on defenders saves him from tackles. Think of him as a bullet. A bullet cannot be stopped by walls of cement or concrete though the material of bullet is weaker than that of cement.The another player with similar play style is Kaka. He too is aggressive towards the defenders. Kaka is a yard faster than Messi and is about 17 cm taller. He also has a longer stride than Messi. Kaka however lacks the short center of gravity that Messi has. His career became plagued with injuries because his play style made him very vulnerable. Him being 187 cm did not help. Kaka’s longer stride made him an easy target for hard and fast defenders. Kaka’s decline is due to his approach towards the game. He was equally aggressive towards the defenders but could not sustain himself because of his physique. He was already 28 when he arrived at Madrid. His physique which made him a beast during his younger years at Milan haunted him at Madrid and later Milan. If Messi could be an analogy to bullet, Kaka would be analogous to a small pocket knife which moved at very high speeds at its prime.