Police spokesman Sgt. David Schlosser says the officer was taken to a hospital Saturday evening for treatment of injuries to his face.
Protesters have clashed with police as officers pushed them out of the last section of McPherson Square, a park under federal jurisdiction near the White House.
By Saturday afternoon, seven were arrested. Schlosser said more may have been arrested in the most recent scuffle.
Police have been clearing away tents they said were banned under park rules. Officers used barricades to cordon off sections of the park and checked tents for camping gear.
