That's right Cheery, but I think that physical attribute didn't start until Men At Arms - or maybe Moving Pictures, as that's the first one Detritus had a featured cameo role and first met Ruby of course. The other trolls in that were fairly smart and mostly did stunt work, though Rock and Flint were aspiring to bit parts...
I think one of the first things that Terry wrote about Detritus and Ruby as a couple was how dopey Detritus was when Ruby said he should be bringing her pretty oo-grah meaning flowers and he obediently went and got her a whole tree though it wasn't completely down to him as oo-grah just means any leafy plant

So the inference of dragging knuckles is there in spirit