If you're in an airport with the back-scatter scanners, they might be able to scan you that way (if you're okay with that). I believe that hip replacements don't set those off and the only requirements for using them are that you be able to stand with your arms above your head for about a minute.
I'm a wheelchair user so I get the pat down every time. Usually it's pretty public and in an area where I can see my bags go through the x-ray machine. The pat downs have gotten more thorough (including checking the inside of pant/skirt waists) since the back-scatter scanners came into effect and, sadly, even if you're getting a pat down for a reason that doesn't involve setting off a scanner, you get the more thorough pat down. You can request a private area if you'd like, but I generally wouldn't bother for a normal pat down. If you're female, wearing a skirt (no stockings, but socks are okay) will speed up the process slightly as then they don't have to pat down where they see skin. For everyone this is also true about short sleeved vs. long sleeved shirts.
Since I'm still in the same area as "normal" security for the pat down, if I have friends or family with me they just go through the normal metal detector and wait for me with our carry-ons. Personally, I wouldn't ask anyone else to go through a pat down just because I need one. They're not the worst thing I've ever experienced (although I once had a truly horrid experience in Charles de Gaulle, but that wasn't US TSA and was before the new scanners), but they're not fun and they are a bit intrusive.
Do plan for it to take up to 15 minutes longer to get through security because they may have to call for someone to do the "assist". (I don't know if you're male or female, but I almost always have to wait for them to get a female TSA agent over to do my pat down and that can take 5+ minutes.) Also, until you're cleared, you can't touch any items of yours that have gone through x-ray and you can't touch other members of your party who have already been cleared. If you're traveling solo and are moved to an area where you can't see the x-ray belt, you can ask the TSA agent to grab your things off the belt for you and bring them to the area.