Hello @nancyjw, Welcome to Mayo Clinic Connect. You will notice we moved your post to this existing discussion Post Knee replacement mobility - so that you can meet other members with similar symptoms and learn what they have shared. You may also be interested in the following information:

Treating Stiffness After Total Knee Arthroplasty: A Technical Note and Preliminary Results:
-- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3414723/

"Joint stiffness is a common, debilitating, age-related symptom, which may be seen after total joint replacement (TJR). Stiffness also occurs in fibrotic conditions such as shoulder capsulitis and Dupuytren's contracture. We speculated that the two traits (TJR and fibrotic disease) are linked pathogenically." excerpt from the following article:
Joint Stiffness Is Heritable and Associated with Fibrotic Conditions and Joint Replacement:
-- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4509645/

@nancyjw you mentioned you are 4 weeks out from the replacement. Have you discussed the stiffness with your surgeon or care team? I had a lot of the swelling and some pain for a short time after the knee replacement and my surgeon told me I was not elevating and icing the knee enough. I also was faithful with the daily exercises but was not keeping the leg elevated when I was sitting for long periods of time.