SA man knocked unconscious on night out

A man is being treated for serious head injuries after he was knocked unconscious in Adelaide's CBD.

He was taken to the Royal Adelaide Hospital for treatment just after 9.30pm on Saturday.

A 20-year-old man from Hackham West and a 17-year-old boy from Port Noarlunga have been charged with aggravated assault to cause harm.

They were bailed to appear in the Adelaide Magistrates Court on 6 April and Adelaide Youth Court on 16 March.