@janicemmccarthy I have had two TKRs but never had the tight feeling that so many people mention! I wish I could be of some help but this is an area where my only knowledge is that I have seen on here on Connect.
I doubt that collagen pills would hurt but I would definitely run it by your orthopedist or any other doctor whose care you are under. I have to run everything by my transplant team because I am post-liver transplant. Is collagen similar to glucosamine and chondroitin supplements? I did try one of those at one point prior to having TKRs but found them to be of no help. Some people do get relief from them though.
Again, give your doctor a call and ask if he would suggest any of those OTC supplements. I can't remember who the orthopedic doctor was whom I was seeing back then but I do recall he said that some people do get help from those supplements. Whether it's a placebo effect or not is questionable.
JK