The victims -- two soldiers and one border police officer -- were evacuated for medical treatment after the incident at the Tapuah junction south of the northern city of Nablus.
The alleged assailant was "receiving medical care," the army said, without providing further details.
It was the latest in a wave of Palestinian knife, gun and car-ramming attacks since October 1 and came as US Secretary of State John Kerry arrived for separate talks with Israeli Prime Minister Benjamin Netanyahu and Palestinian president Mahmud Abbas.
Around half of the Palestinians killed have been alleged attackers. Others have been shot dead during clashes with Israeli security forces.
