Knee Smash

From SmashWiki, the Super Smash Bros. wiki

Not to be confused with the first hit of Solid Snake's forward tilt, which can be used to perform the Knee Lock.

The Knee Smash, also known as the "Knee of Justice," or the "Ultimate Knee!", is Captain Falcon's forward aerial in Melee and Brawl. (In the original, it was what is now Falcon's N-Air, and his N-Air in SSB64 was a sex kick.)

It is an extremely powerful killer that sends the enemy at a low trajectory. This move is considered by some to be the best move in the game, due to its short lag time and powerful knockback ability. Most combos and strategies end with a knee, which deals up to 18% in Melee and 20% in Brawl, under NORMAL circumstances (i.e. NOT Giant status).

The Knee Smash has two main hitboxes: the initial, much more powerful hitbox, and the second, much weaker hitbox. The initial hitbox (only a few frames in length) is the primary killer in Captain Falcon's arsenal. It is accompanied by an electrical pulse. The second hitbox lasts much longer, but it lacks most all the power of the initial hitbox. Its knockback is minimal, so many use it as a precursor to a successful follow-up true Knee Smash.

In Brawl, the knee is much harder to land, and its knockback power has decreased slightly. If a true Knee Smash is landed, the hitstun lasts about a second, much longer than in Melee.

Interestingly, Ganondorf's Forward aerial is not a knee, instead being more of an arcing downward punch resembling Mario's. (in both Melee and Brawl). However it has the same amount of startup frames as Falcon's Knee.

It should be noted that "Knee Smash" is not the only term for this attack, other popular options being "Knee of Justice" and "Electric Knee". "Knee Smash", however, is Nintendo's official name for the move.