Yes, JOYSTICK is a Scrabble word!

Letter values in Scrabble US: J 8, O 1, Y 4, S 1, T 1, I 1, C 3, K 5.

Is it a valid word?

JOYSTICK is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a lever used by a pilot to control the ailerons and elevators of an airplane
a manual control consisting of a vertical handle that can move freely in two directions; used as an input device to computers or to devices controlled by computers

Also: control stick.