Like the non articulated sort from the 14thc.?
http://www.mbs-brasses.co.uk/Metwold%20mid%20scaled.jpg
The standard solution seems to be to simply run a lace through them, but this doesn't seem to be the period solution.
I was considering riveting a leather tab to the inside of the poleyn, then lacing that to a tab at the bottom of the cuisses.
(I've seen reproduction armour that has the right look, but IDK how they did it.)
Thanks!

There are effigies with poleyins and greaves without cuisses. So they weren't laced to them . I think that they were simply laced around the leg and lean on the greaves thanks to the force of gravity.

but if they are not pointed they tend to fall or move out of position. i've worn with just a simple strap behind the knee and they walked all over the place. I have had thoughts that they were either pointed on the sides or the top in some way or another. could have even been attached to the padded chausis that goes underneath it. but it's pure speculation as to there are no known ones still attached that I know of.

It seems to me that in the absence of hard evidence, "technological fashion" wins out. 14th c. Europeans pointed everything.... the number of grommets that they must have sewn...

Given that only slightly later we see whole harness assemblies (arms, legs) being pointed, surely that's the most logical interp?

But I too would like to know if there's a hard answer. Likewise, for the Italian style round paulder--was that laced/pointed on? Did they point straight through the maille?

Well, I was referencing the sort from the mid 14thc, like posted above.
It's shown with a line of rivets on the poleyn overlaping the rivets in the cuisses, any what they were utalized for?