Why is Brad Pitt on a cane?

It was a mystery to rival any Hollywood movie - why was superstar Brad Pitt using a cane?
He attended the Palm Spring Film Festival, hobbling and with a walking stick.
On the red carpet, even good friend George Clooney was concerned.
SOUNDBITE: George Clooney on Brad Pitt, saying (English):
"Yeah, you're right. You know, Brad's supposed to be here sometime. I hear he's in a cast. I want to know what happened."
What happened, it seems was that the "Moneyball" actor tore his ACL.
He told People magazine he was carrying his daughter Vivienne down a hill and slipped.
Still, the actor and his partner Angelina Jolie answered reporters' questions.
SOUNDBITE: Brad Pitt, on being honored at The Palm Springs International Film Festival, saying (English):
(Reporter: Brad, what's more stressful raising six kids--) Six kids. I know the answer to that."
SOUNDBITE: Angelina Jolie On Directing Another Film, saying (English):
"I'm still so shy to even consider myself a writer-director. But I think I'm so driven by something that I care about. So I'd have to do that."
At the ceremony, he took home a "Desert Palm Achievement for Acting" award.
SOUNDBITE: Brad Pitt Giving Acceptance Speech, saying (English):
"This is a great honor for me. You know, like, that you would acknowledge these two films, 'Moneyball,' and 'Tree of Life.' Like many of you here, I haven't seen 'Tree of Life' yet. But I hear we're really good."
Clooney took home the night's biggest honour - the "Chairman's Award".
SOUNDBITE: George Clooney Giving Acceptance Speech, saying (English):
"But the truth is, and we don't really want to tell all those guys. we would do this for free. It's a fun thing to do. Most people don't get it."
Actress Glenn Close was honoured with the "Career Achievement Award."
She currently stars in the critically-acclaimed film "Albert Nobbs" for which she's already received a Golden Globe nomination.
SOUNDBITE: Glenn Close, on her role in "Albert Nobbs," saying (English):
"And this is a particular hard sell this movie. It's a great story, and the character is like none I have ever seen in any other movie. And, so, the fact that we finally did it. And we did it with the people involved, was a miracle."
For Britain's very own Gary Oldman it was also a successful start to the awards season.
He took home the International Star Award for his role in "Tinker, Tailor, Soldier, Spy".
SOUNDBITE: Gary Oldman, actor, saying (English):
"This is one of the, one of the great, great projects, great roles. They don't come along often. With this director, with this cast. You take these when you can get them, because they are few and far between."
Other winners included Charlize Theron and French director Michel Hazanavicius for "The Artist".
Cindy Martin, Reuters