In reply to andyfallsoff:
> would be good to hear what is worth doing / visiting in the surroundings.
There are some impressive show caves, some with amazing cave paintings, of which Niaux has some of the finest:
http://www.sites-touristiques-ariege.fr/sites-touristiques-ariege/grotte-de... They do guided tours in English, but you normally need to book in advance.
Montségur, the last stronghold of the Cathars, is well worth a visit.
I guess the knee will rule out any serious walking too, but for some great views with little effort or height gain, you can drive up to Plateau de Beille and wander along the tracks heading south-east for a bit.