Great to find a different type of Rider on the forum, and another UK based. I know Thorn make some great bikes but That Rohloff is not something I would have contemplated for Distance riding a long way from civilisation. Not many mechanics in The middle of no-where and even less to know about repairing them. BUT I know they have a good reputation for reliability.
On the knee problem- Haven't had cartilage problems but have suffered with knees- The quad muscles are vital to keep the knees in shape but as I found out- do not forget the rest of the body- After a 6 month lay off- I found a local gym and although I was in recovery training- I did manage to build up the rest of the body that had wasted in the period I was off.
Good luck on the recovery
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How long was I in the army? Five foot seven.
Spike Milligan