Son injured by knife in domestic dispute

A 12-year-old boy has been cut as he intervened in a domestic dispute between his mother and knife-wielding father in Sydney's southwest.

Police attended a unit at Clifford Avenue, Canley Vale, after the man allegedly threatened a 45-year-old woman with a knife about 5.30pm (AEDT) Tuesday.

The woman ran out of the unit into a stairwell where the man, 47, allegedly pinned her against a wall while armed with a knife, police say.

The couple's son, 12, suffered cuts to his foot as he tried to intervene.

The man was arrested and charged with five offences including assault occasioning actual bodily harm.

He was served with an apprehended violence order and was refused bail to appear in Liverpool Local Court on Wednesday.