Hi, thanks for writing to HCM.
This is just to educate you that no pain should be felt in the operated knee after 3 months of a successful total knee replacement
(TKR). The very fact that you have little trouble in getting up and down the stairs (after 5 months) indicates that there is something wrong in the joint.
There are numerous causes that produce pain after a TKR surgery. Infection can be ruled out in your case as your pain is only related to movement of leg and is not present at rest. Pain associated with mechanical activity is often due to inflammatory causes or mechanical derangement.
So a detailed evaluation is necessary to pin point the cause of your pain.
Hope this information is helpful. Good day