Leni Klum flaunts her slender arms at her 20th birthday celebrations

Klum also posted a throwback clip of Leni as a baby in a sweet birthday tribute to her oldest child

The 19-year-old model - who will turn 20 on May 4 - had on a white tank top and a beige silk camisole in two of the images. The focus was on the gems from Yurman.