Crocheting the cuff onto the knitted piece

Hi everyone!
I’m a little stuck right now...
I’m currently knitting a sweater and want to crochet the cuffs using post double crochet.
For the lower ribbing, I started with the post double crochet and knitted the sweater up from there. 
For the sleeves, I’ve now done it the other way around and have to crochet the cuff onto the knitted fabric. Do I need to bind off the knitted fabric first, or can I work the crochet stitches directly off the knitting needle?

Well, I would bind off first, then crochet a row of half double crochets or double crochets into my bound-off stitches, and then continue with post double crochets in the next row. It’ll definitely look cool—crochet and knitting combined.

I’d also bind off first. Working directly off the needle might make it too “loose”....

Thanks for your quick replies! Yes, I bound off and then crocheted the cuff onto it. Unfortunately, I can’t upload pictures to threads, but I’ll post one in the gallery once the sweater is finished.

I’ve uploaded a picture of the cuff to the gallery.