Hi Chris,
there is a very little possibility that one aberation of Cantharis rufa shows the more or less similar colouring in the knees. But this possibility is very, very small. I haven't seen it yet by a number of far more than 100 specimen from between 10 and 20 different habitats.
At least you are right. I should have told that this is not absolutely for sure, but the chance of C. rufa in this colouring is not 1%.
Thank's for giving this correction.
Regards
Klaas