Police say a woman ran over her partner's son who then smashed her car with a child's scooter.
The woman, 27, allegedly struck the 24-year-old son of her partner with her car outside a Masterton address, spraining his ankle.
The man then reacted by picking up a child's scooter, striking the woman's vehicle several times with it, police say.
Sergeant Mike Sutton said the incident started out as an argument between the two at 10am on Friday at the Vivian St address of the woman's partner and his adult son.
''The [alleged offender] has then got in a vehicle and driven the vehicle at the victim, hitting him and knocking him over.''
The victim then got to his feet, picked up a child's scooter and started striking the woman's car with it.
Police were called soon after by the woman as she drove from the property, Mr Sutton said.
The man was later taken to Wairarapa Hospital where he was treated for the sprain.
The woman was arrested and charged with assault with a blunt instrument and will appear in Masterton District Court at a later date.
Mr Sutton said police were considering laying a charge of wilful damage against the 24-year-old man.