DEMI tells pal JEN  ANISTON to get some DRASTIC PLASTIC!

Plastic surgery fan Demi Moore is telling a shaken Jen­nifer Aniston that she needs to have work done on her legs, say sources.

Jennifer, 44, prides herself on staying in top shape and was said to be lapping up compliments about her sexy physique on the New York set of “Squirrels to the Nuts” – until she took a call from her longtime friend Demi.

Demi’s candid advice hit Jennifer like a sledgehammer because the former “Friends” star wants to look perfect for her upcoming wedding to Justin Theroux.

“Jennifer has always ap­preciated Demi because she does not hold back her opin­ions,” said a close source. “But she wasn’t happy when Demi told her she needed her knees fixed. Demi even gave Jen the number of her plastic surgeon.

“Now, Jen’s por­ing over photos of her knees, wondering if there’s something wrong with them.”

The source adds that Jennifer worked out like a madwoman to play a stripper in her new movie, “We’re the Millers,” and she’s still the same size she was during filming.

“Still, she’s copying paparazzi photos from the Web and magnifying them on her computer so she can exam­ine her knees,” continued the source. “She thinks they look pretty good, but there is one long wrinkle above both knees that she’d like to address.”

But Jennifer’s fiancé Justin thinks she’d be crazy to fol­low the knee-jerk advice of 50-year-old Demi, who is said to have spent hundreds of thousands of dollars on her body.

Before she filmed “Char­lie’s Angels: Full Throttle,” Demi reportedly underwent a full body lift, including knee surgery to remove sag­ging skin from the area.

Revealed a pal of the actor: “Justin thinks Jen is perfect, and the only thing wrong with her are some of her friends.”