Options
Every knee replacement makes a few design choices. None is best for every patient, and for most of them the research finds small or no differences. Your surgeon's experience with a system, your bone quality, your ligaments and your anatomy all shape the choice.
Cemented implants are fixed with bone cement and are stable immediately. Cementless implants have a porous surface, often 3D-printed titanium, that the bone grows into over the following weeks. Cementless use in the US roughly tripled between 2016 and 2022.17
The posterior cruciate ligament (PCL) can be kept (cruciate-retaining) or removed and replaced by a post-and-cam mechanism in the implant (posterior-stabilized). Newer "medial-congruent" or "medial-pivot" inserts use a deeper inner side to provide stability with or without the PCL.
Cochrane (17 RCTs, 1,810 patients): range of motion 2.4 degrees higher and functional KSS 2.3 points higher with PCL sacrifice, judged clinically irrelevant; no difference in pain, WOMAC or complications.18
In a fixed-bearing knee the plastic spacer is locked to the tray. In a mobile-bearing knee it can rotate slightly, which was designed to reduce wear. Most US knees are fixed bearing.
The back of the kneecap can be covered with a plastic button or left natural. Practice varies widely between surgeons and countries.
Femoral components are usually cobalt-chromium alloy; some use oxidized zirconium or a ceramic-like coating, which can matter for people with metal sensitivity. Tibial trays are cobalt-chromium or titanium alloy, and cementless versions often use porous titanium. The spacer is ultra-high-molecular-weight polyethylene, often highly cross-linked and sometimes blended with vitamin E to resist oxidation. Ask your surgeon which materials your implant uses.
Considering a partial instead of a total knee? See partial vs total knee replacement.