Can you cleanse out of knock-up's or knocked-backs?

For champions like Alistar, Orianna, Lee Sin, Gragas etc can you cleanse out of their ultimate's/skills?

All displacement type spells (knock-back, knock-up, pulls, etc) cannot be prevented or ended by the use of Cleanse. Additionally, these type of spells are not affected by Tenacity. The only other form of Crowd Control that is not effected by tenacity or cleanse is Suppression, such as Warwick and Malzahar's ultimates.

However, it is worth noting that there are ways to prevent these types of spells, such as Sivir or Nocturn's shield, Morgana's Black shield, or Banshee's veil.

A lot of information about the varying effects and counters of Crowd Control types can be found here: http://leagueoflegends.wikia.com/wiki/Crowd_control

No you cannot, they are nearly instantaneous and are displacement abilities. It would be like asking if you can cleanse out of Janna's ultimate. It just pushes you or pops you up, knockups require the champ to be next to you/very close making it difficult to land them - so easily manageable.