Welcome @perilousowl, You will noticed that we moved your post to the following discussion on the same topic so that you can read what others have shared on the question of trouble sleeping after knee replacement. If you click the link below it will take you to the beginning of the discussion where you can read what others have shared.

--- Trouble sleeping after TKR: What helped you sleep?: https://connect.mayoclinic.org/discussion/trouble-sleeping-after-tkr/.

One of the things that helped me was wrapping a flexible cold pack in a towel and putting it under my knee and leg when I go to bed. Sometimes I used a cold pack that I've used a little earlier in the evening and it's not quite as cold but still pretty cool when pressed against the leg. @ellerbracke @contentandwell @debbraw @doodles418 and others may have some suggestions for you also.

Does knee pain play a part in your insomnia?