Patrick Schwarzenegger tweeted Saturday that he received stitches "down the back and but" (sic) after the accident, and he also thanked doctors who he said cared for him in Sun Valley.
He provided a link to a photo he posted to the social networking application Instagram, showing a deep cut on his lower back. He also said that he had been bruised in the accident, but did not provide details on how he got injured.
A spokesman for Shriver did not provide further details.
In 2006, Arnold Schwarzenegger broke his leg in a ski accident at Sun Valley while he was governor of California.