knuckles
Tenía los nudillos blancos de apretar tan fuerte el volante.
His knuckles were white from gripping the steering wheel so tightly.
Come, o te daré un sándwich de nudillos.
Eat, or I'll give you a knuckle sandwich.
— Die Fälscher (2007)
Digamos que tendré que darle en los nudillos.
Let's just say I'll have to hit him in the knuckles.
— Pacto de sangre (1944)