Brad Pitt's mystery knee injury has been solved - the actor hurt himself protecting his daughter from a fall while skiing.

The Ocean's Eleven star limped along the red carpet with a cane at California's Palm Springs International Film Festival Awards Gala, where he picked up a top prize on Saturday (07Jan12).

It was previously reported that Pitt sought medical advice after tearing a ligament, and now his partner Angelina Jolie has revealed the heroic movie hunk twisted his knee rescuing his daughter on a family ski vacation.

Pitt was carrying three-year-old Vivienne and took a tumble on the slopes as he attempted to ensure she wasn't hurt.

Jolie tells OK! magazine, "Vivi's okay. She was absolutely fine. He took the fall. It was just to make sure.

"When (eldest son) Maddox was younger, I took a fall and cracked my elbow because I wanted to make he wasn't injured... Every parent will stand in the line of fire for their kids. It's quite a normal thing".