Probably tie rod ends or maybe ball joints.
Oh, it IS that and more - the bushings in those areas too..
Easy to know when it's time to do some major front-end maintenance. Go over a bridge deck joint (and with rare exceptions, DOT crews or road construction firms have NO CLUE how to match up a road surface to a bridge deck) and if the steering wheel does a brief 'shake', it's time to head for the shop..
I just got my F-350 back on Friday morning. A few days earlier I noted a brief shake going over a bridge deck and called the shop post haste..
Total for the front-end repair was about $1300 - paid for by Ford's ESP.. This was a 53K on the odometer.. Previous (2004) truck needed it at 30K but the front-ends back then weren't quite as beefy..