Some pitchers throw a regular curveball as their breaking pitch. Others throw a knuckle-curve.
A knuckle-curve, sometimes called a spike curve, is a variation of a traditional curveball, where the pitch is generally gripped and thrown like a curveball but with one knuckle raised off the baseball. The modern knuckle-curve has curveball movement, with an up-and-down trajectory and often horizontal break toward the pitcher's glove side as well.
The knuckle-curve sounds like one of baseball's greatest paradoxes, given that a curveball is defined by its spin and a knuckleball is defined by its lack thereof. Still, the knuckle-curve produces the desired effect of the two pitches -- a slow, curveball break mixed with some of the unpredictable fluttering of the knuckleball.
For those pitchers who have mastered it, the knuckle-curve is a deceptive weapon, often stashed away until they think a hitter will be fooled by it.
The basic premise of the knuckle-curve is that at least one of the pitcher's fingers (usually the index finger) is bent while holding the ball -- like a knuckleball -- while the pitcher maintains the snap of the wrist that is synonymous with a curveball.
The most common knuckle-curve grip features the nail of the index finger dug into the baseball with the knuckle raised in the air off the ball, while the pitcher's middle finger rests along the baseball, often on one of the seams.
Think of the pitch as a spectrum between a knuckleball and a curveball. For pitchers today, who emphasize the curveball aspects of the pitch (bending one finger so that a knuckle is on the ball), a knuckle-curve is basically just a curveball that spins and moves slower. And for pitchers who emphasize the knuckleball aspects of the pitch (gripping the ball like a knuckler, while ever-so-slightly snapping the wrist), a knuckle-curve is basically just a knuckleball that spins more and moves faster.
Nowadays, a knuckle-curve is essentially just a form of the curveball. A curveball and a knuckle-curve function the same way for a pitcher, and pitchers will generally throw either one or the other depending on their preference for their curveball grip.
But over the course of baseball history, because some knuckle-curves were so close to a regular knuckleball and others were so close to a regular curveball, the pitch existed for years while simply being identified as one or the other. It's quite possible that Ed Summers, who pitched for the Tigers until 1912, was the first to throw the knuckle-curve regularly, as he was well known for the varied deliveries and movement on his knuckleballs.
In A Call
"slow curve," "spike curve"