The first, more modern and commonly used pitch called the knuckle curve is really a standard curveball, thrown with one or more of the index or middle fingers bent.
This version of the knuckle curve was used by Major League pitchers Phil Hughes and Brad Peacock in the 2010s.
Justin Verlander formerly threw a knuckle curve but was forced to abandon the pitch due to problems with blisters.
The most famous practitioners of this type of knuckle curve are Burt Hooton, who pitched for the Chicago Cubs and the Los Angeles Dodgers from the mid-1970s to mid-1980s, and former reliever Jason Isringhausen.
The pitch would be perfected by Chicago White Sox legend Hoyt Wilhelm during the later stages of his career, after flirting with it for most of his time in the majors.