”Doctor, how many months do I have to stay in bed after my joint is replaced?” This is a question that I am often asked in my clinical practice. First of all, what we call “joint replacement” surgery does not involve cutting out the entire joint and replacing it with a new one, but rather removing the damaged part of the joint surface, especially the cartilage, and replacing and reconstructing it with artificial joint technology, with the patient’s own bones preserved to the greatest extent possible. Secondly, with the development of artificial joint technology, the artificial joint components are more and more tightly fixed to the patient’s own bones, which is more and more conducive to the patient’s early removal from the floor. The most commonly used fixation methods are: 1. Bone cement Bone cement is a polymer, which is commonly called bone cement, but it is not the same thing as the cement used in construction, as a filler it can provide good fixation and stability between the artificial joint prosthesis and the bone. Bone cement obtains mechanical stability at the interface by micro-interlocking with the bone bed and is particularly suitable for knee replacements and elderly or severely osteoporotic patients. With the advancement of bone cement technology, the long-term effect of bone cement fixation has been further improved, and bone cement-based prosthesis is still the gold standard for evaluating other new prostheses. 2, biological fixation Biological prosthesis is also known as non-cemented prosthesis, that is, no bone cement is used, the prosthesis is in direct contact with the bone, the surface of the prosthesis adopts porous structure, after implantation the surrounding bone grows into the pores of the porous surface of the prosthesis, forming an osseointegrated connection between the bone and the prosthesis to achieve permanent stability of the prosthesis-bone interface. Biological prosthesis fixation must obtain reliable initial stability, and the contact between the prosthesis and the bone surface should be tight and without micro-movement, which is a prerequisite for achieving biological fixation. To promote bone growth on the prosthetic surface and enhance osseointegration, hydroxyapatite and tricalcium phosphate ceramic materials are often coated on the porous metal surface to promote osteoinduction, and some biological factors (such as BMP, TGF-b, etc.) can be loaded to increase the speed of bone growth into and the strength of integration of bone and prosthesis. Finally, the sooner the patient is able to move around, the better the patient’s recovery and the prevention of complications such as blood clots. Therefore, for our patients with initial surgical joint replacement, we usually let the patient walk on the ground and exercise on the second or third day after surgery. There are some reports of patients getting off the floor a few hours after surgery, which is not a big problem in terms of the stability of the prosthesis, but the patient’s walking steps may be unstable, and because the time to walk after joint replacement is long, these early hours are not very necessary.