A Frankston North woman says she will need plastic surgery after a pitbull ripped off her cheek.

Emma McKnight, 37, said her dog, a Staffordshire bull terrier cross, was attacked during a Sunday morning walk when a pitbull came out of a gate of a Rosemary Crescent home in Frankston North.

She said she shielded her dog and the pit bull latched onto her arm.

"It lock-jawed onto my arm, I tried to get it off and it went for my face and took the cheek off my face," Ms McKnight told radio station 3AW.