A 24-year-old NSW woman with stab wounds was rescued from the boot of a car after a motorist noticed her hand waving from the rear taillight.

The motorist was travelling down the Hume Highway at Pheasants Nest on Wednesday morning when they saw the hand waving and called Triple 0.

Police stopped the car – a white Holden sedan – at 11.50am at Berrima, and found the woman in the boot.

She was treated for her multiple stab wounds at the scene before being taken to Liverpool Hospital with non life-threatening injuries.

Two other women, aged 24 and 18, were arrested and taken to the Southern Highlands Police Station.

An investigation is underway, with anyone with information urged to contact Crime Stoppers.

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