It happened Sunday night on northbound Highway 33 near Douglas avenue.
Investigators say 27-year-old Jose Morales Gutierrez of Mendota was speeding and rear-ended the officer's motor unit.
Officer Rodolfo Tabares suffered injuries to both his forearms and lower extremities, but doctors say he is expected to make a full recovery.
Gutierrez was arrested and booked in the Fresno County jail on suspicion of DUI causing injuries.