Serious crash injures Sydney motorcyclist

A motorcyclist is in hospital with serious head, arm and spinal injuries following a crash in Sydney's south.

A car and a motorbike collided at the intersection of The Kingsway and Sylvania Road about 5.40pm on Wednesday, police said.

The impact threw the 22-year-old male rider from the bike and he was treated at the scene by paramedics and taken to St George Hospital in a critical condition.

He is reportedly in a serious but stable condition with multiple injuries to his head and body, including spinal injuries.

A 38-year-old man driving the car and his female passenger were not injured, but the man was breath tested at the scene and returned a negative result, police said.

He was arrested and taken to Sutherland Hospital to undergo mandatory blood and urine testing and police have appealed for witnesses to contact Crime Stoppers.