Hello and welcome.
My name is ***** ***** I will be glad to assist with your two questions.
I"m sorry you did not receive an earlier answer; your patience is greatly appreciated.
First, because you are planning to travel internationally. it would be most economical for you to apply for Global Entry or "GOES," this program affords all the benefits of TSA Precheck, and for only an additional $15, you can include Precheck in your GOES application.
You can start the online application process here:
As for the liquid supplement for your knee, there will be no problem, because it is for medicinal purposes and not subject to the normal regulations for the amount of liquid you can bring in your carry-on. Getting a letter from your doctor on his/her letterhead, explaining the reason for this liquid supplement for your knee.
Passengers with medical problems or disabilities, benefit from TSA Cares, a department that helps passengers when they enter the airport. You can contact them 72 hours before your flight, at:
1- 855- 787- 2227. You can also contact TSA's Passenger Support for help with getting through security. Ask for their number from TSA Cares, as almost all the TSA sites are having a problem right now, so I can't connect.
I hope this helped and wish you a wonderful trip!
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