Code for knee grow, with patella substituted for knee and expand substituted for grow. It is a subtle way of saying negro or to otherwise refer to an African American in a coded way.
Cori: "Who am I looking for?"
Craig: "He's right there."
Cori: "Who? Which person?"
Craig: "The . . . uh . . . patella expand."
Cori: "Oh, I see; he is right there . . . "