The incident happened around 10:30 p.m. Tuesday on the southbound side of the freeway near the 8th street exit in downtown Los Angeles.
The California Highway Patrol said a witness called 911 to report an attempted kidnapping after seeing a woman trying to get out of the vehicle.
Authorities said there was an argument between a man and the woman.
The man pulled out a knife, but the woman was able to get it away from him and throw it from the vehicle.
Both the man and woman somehow ended up out of the vehicle and on the freeway.
"The vehicle continued southbound on the 110 without anybody in it. It came to rest up against the center divider," said Sgt. Mike Hernandez of the California Highway Patrol.
Both people were taken to the hospital with moderate injuries. The knife was recovered.
It's unknown if any charges will be filed.