Knuckle curveball
A knuckle curve is a type of curveball thrown by bending the index finger into a knuckle-like position.
Despite what the name suggests, it does not have the same unpredictable movement as a knuckleball.
While the movement is essentially the same as a standard curveball, bending the index finger prevents it from interfering with the ball, making it easier to “take something off” the pitch.
Because this grip makes it easier to “take something off” the pitch, it can result in better release and, in some cases, greater break.
However, easier release also means a higher risk of losing control of the ball.
The pitch can slip out unintentionally, making it more difficult to control.
As a result, the knuckle curve requires practice and careful handling.
Grip and Release
Start with a standard curveball grip, then bend your index finger like a knuckle and place the nail side against the ball.
Alternatively, you can keep the finger bent and plant it more upright on the ball.
Like a knuckleball grip, this can feel cramped if your fingers are short, so a certain hand size or finger length may be helpful.
The release is the same as a standard curveball.
Use a “coming over the top” arm motion, following the imagined trajectory of the pitch.
At release, your wrist should naturally rotate so that the back of your hand faces outward.
At the moment of release, use your middle finger (on the seam) to brush over the top of the ball, focusing on letting the ball “roll off” your finger.
Because the grip is less stable than a standard curveball, overemphasizing the “let it go” feeling may cause the ball to slip out unintentionally.
This is not a knuckleball—you do not push the ball with your fingernail.
The index finger acts only as a guide to control the direction and release of the ball, not to generate spin.
Keep the index finger relaxed and lightly in contact with the ball.