I would suggest TKD only if you go to a reputable ITF school. Go and watch an advanced class. If you see little kids with black belts that can't do anything, walk out and find a new school. Don't do WTF because it's more competition and sport based, rather than traditional.
Karate is also a very respectable martial art, but it demands more balance and flexibility.
ITF TKD is the way to go.