"Little ski accident today. Some bruises and sitches down [my] back and butt," Patrick wrote in a photo caption. "Thanks to the Sun Valley doctors for everything."
Arnold Schwarzenegger and Maria Shriver's eldest son also uploaded a graphic photo of the deep cut just above his right butt cheek, showing his bloodstained underwear.
Patrick, a part-time model, is currently a senior at at Brentwood School in L.A. He also has his own clothing line, Project 360, which helps raise money for various charities. Though he's interested in acting, he's also hoping to further his education.
"I'm applying to USC, Georgetown, Stanford and Penn. One sister goes to USC and the other to Georgetown," he told WWD in 2011. "If all my work is going well and I get into USC, that's probably what's realistic for me."