The winger took a shot to the hand from Capitals defenseman Jonas Siegenthaler during the first period of the game and immediately went to the locker room and did not return.
Van Riemsdyk has 19 goals and 21 assists for 40 points in 65 games this season. He has been on the Flyers' third line during their winning streak that has vaulted them up the standings.
The Flyers have recalled rookie Joel Farabee from the minors to replace van Riemsdyk beginning with Philadelphia's home game Thursday against Carolina.
The Flyers (39-20-7) stand second in the Metropolitan Division, a point behind the Capitals. They finish the regular season April 4 at Buffalo.