Van Riemsdyk was hit in the left leg by a shot during the first period against the Dallas Stars on Sunday. He limped off the ice and did not return to the game.
After the game, Blackhawks coach Joel Quenneville described van Riemsdyk's injury as "pretty bad" and said the defenseman would be out "awhile." The Blackhawks placed van Riemsdyk on long-term injured reserve Monday.
Van Riemsdyk, 23, who is the younger brother of Toronto Maple Leafs forward James van Riemsdyk, was the surprise of the Blackhawks' training camp and leaped a number of the organization's defense prospects to be included in Quenneville's season-opening roster. Van Riemsdyk's role and ice time had increased recently. He played a season-high 21:04 in the game prior to his injury.
Van Riemsdyk suffered a left ankle injury at the University of New Hampshire last season and missed the team's final 15 games. He signed a two-year deal with the Blackhawks on March 24.
He has one assist and a plus/minus of zero in 18 games. He's averaged 13:32 of ice time.