Hi
Welcome to Hip Talk.
I did not have my knee pop, but many people have problems with their knees after hip resurfacing surgery. The new hip is now in original condition and your body is not use to that. It has put up with a problem hip and in many cases a somewhat shorter hip due to the loss of cartilage and bone on bone situation. So the back, knees and other hip have to start to adjust.
Also when they dislocate your hip for surgery, they may possibly have put some extra strain on the knee. So the knee has to get back to normal.
For the best answer, just give Dr. Su's office a call and ask what might be causing the problem. He will give you a better answer than all of us non-medical people. Dr. Su is a great doctor. He has provided my webstie with good articles to help people learn about hip resurfacing topics.
Good Luck. Your boyfriend is really in the early stages of recovery and he will feel many things changing in his body. He has been thru major surgery and that is very difficult. Many of us are lucky and have quick and easy recoveries - but the body still takes a lot of time to heal.
Please stay in touch and tell your boyfriend we wish him good luck. I look forward to getting a story to post on the website.
Pat