There are a total of 68 Treasure Chests in Knack. Finding all of these Collectibles will earn you the “King of Adventure” silver trophy. You have to find all treasure chests in one playthrough!
If you miss a chest, there is no way to go back. Getting them via chapter select will not work either. It’s highly recommended to make backups of your save game every couple of chapters (e.g. on USB stick or PlayStation+ Cloud). So in case you miss a chest, you can always go back instead of having to restart the story from scratch. By pausing the game you can see what chapter you are currently in.
The treasure chests are hidden behind breakable walls and contain random gadget parts or crystals. The item you find is totally random and will change every time. Gadget parts and crystals are used to upgrade Knack and will count towards several other trophies. Opening the chests and getting upgrades will also make your playthrough easier. So it’s well worth looking for the chests, especially on your hard playthrough.
Treasure Chests Video Guide