I'm contemplating walking the "Sentier Cathare" in October, a hiking trail 275 km, usually done in 12 days, thus about 23 km/day. Yesterday as part of our preparation Jasper and I walked this circuit around the lake created by the dam (barrage) on the river Agly, nominally 20,6 km but more like 23 since I lost my way a couple of times. Today knees are OK, ankles not.