Washington, May 25 -- Christie Brinkley is standing like a rock by her ex-husband, Billy Joel, following his recent health news.

The 71-year-old supermodel took to her Instagram account on Saturday to share a message for the legendary singer, who had just revealed his diagnosis of normal pressure hydrocephalus (NPH), a brain condition that can cause walking difficulties, memory issues, and balance problems.

In her post, Brinkley shared a video that featured moments from a Billy Joel concert she attended with her daughter, Sailor Brinkley-Cook.

Brinkley said she had been searching for "cute photos" of Billy and their daughter Alexa Ray Joel when she came across the concert clip. The video reminded her not only of their past but also of ...