Your doctor may recommend knee replacement surgery if you have severe knee pain and disability from rheumatoid arthritis, osteoarthritis, or traumatic injury. A knee replacement can relieve pain and help you live a fuller, more active life.
What is deferred action? Deferred action is a discretionary determination to defer a removal action of an individual as an act of prosecutorial discretion. For purposes of future inadmissibility based upon unlawful presence, an individual whose case has been deferred is not considered to be unlawfully present during the period in which deferred action is in effect.
The way I understand it DACA (the Deferred Action for Childhood Arrivals) is the policy action / program introduced by the US government and dreamers are the children who are covered by the act. Some children were brought to the US by parents as infants or toddlers.