Glue and Knee Replacement

Bone Cement for Knee Replacement

“Then I simply glue your new knee parts to the bone.” “Wait, did you just say you use GLUE to replace a knee joint?” That is a real conversation I have had with more than one nervous patient, and it is a fair thing to ask. Yes, I often use what most people would call “glue” during knee replacement surgery. The proper name is bone cement, and bone cement for knee replacement is one of the most studied and most reliable tools in joint surgery. Let me explain what it actually is and why it helps you walk sooner. A knee replacement is really a resurfacing. I reshape three surfaces: the end of the femur (your thigh bone), the top of the tibia (your shin bone), and the underside of the patella (your knee cap). Contrary to popular belief, I remove only a thin layer of bone and leave the rest of the bone and the ligaments around your knee undisturbed. Onto those prepared surfaces I place two thin metal components, one capping the femur and one capping the tibia. A smooth medical-grade plastic (polyethylene) insert sits between them and acts as your new cartilage surface, so metal never grinds on metal. A thin plastic button can also resurface the back of the knee cap. So where does the “glue” come in? Technically, bone cement is a family of materials with a powder phase and a liquid phase. Mixed together, they form a paste that self-sets once it is in place. During a cemented total knee replacement, I use that paste to fix the metal and plastic parts to the prepared bone. Here is the part that surprises people. It works less like household super glue and more like the grout under a bathroom tile. The cement fills the tiny spaces between the implant and your bone, then hardens into a solid, load-bearing layer that locks everything together. We mix the cement in the operating room on an as-needed basis. The powder is combined with a liquid (called the monomer) in a vacuum bowl that pulls out air bubbles and keeps the cement strong. Within a few minutes it firms up from a runny liquid to a frosting-like paste, and then to a hard, stone-like solid. Once it cures, the parts are locked solidly to the bone. That speed matters for you. Because the fixation is immediate, there is no waiting for bone to grow into the implant. The construct is stable as soon as you leave the operating room, which is one reason most of my patients stand and take their first steps the same day as surgery.

What Is Bone Cement Made Of?

Today the standard bone cement is polymethylmethacrylate, or PMMA. You already know this material from everyday life. It is the same acrylic family as Plexiglas. The science is not new. Cold-curing methyl methacrylate was developed in 1936 and first used in dentistry. In the late 1950s, Sir John Charnley, a pioneer of modern joint replacement, refined the cementing technique that surgeons still build on today. Decades later, cement fixation remains the gold standard against which every other fixation method is measured. Bone cement arrives as a powder and a liquid that are combined during surgery. The table below shows what is in each phase.

A breakdown of the chemical components found in the powder and liquid phases of PMMA bone cement.

Powder phase	Liquid phase
Polymer: polymethylmethacrylate (PMMA) and copolymers	Monomer: methyl methacrylate (MMA)
Initiator: benzoyl peroxide (BPO)	Accelerator: N,N-dimethyl para-toluidine (DMPT)
Radio-opacifier: zirconium dioxide (ZrO2) or barium sulphate (BaSO4)	Stabiliser: hydroquinone
Optional antibiotic: for example, gentamicin

What Bone Cement Is Like in the Operating Room

A few details I share with curious patients:

• It has a sharp, fume-like odor, similar to a dry-erase marker.
• The powder is made of tiny bead-shaped particles about 40 microns wide. They contain PMMA plus an initiator (benzoyl peroxide) and a radio-opacifier (such as zirconium dioxide or barium sulphate) that makes the cement visible on X-ray.
• The liquid is mostly MMA monomer, with an accelerator (DMPT) and a stabilizer (hydroquinone) that keeps it from hardening on the shelf.
• Curing is exothermic, which means it gives off heat as it sets. The pace depends on the temperature and humidity in the room.

I sometimes describe the whole process as icing a cake, if the icing were hot, fast-setting, and a little smelly. Antibiotic powder can also be mixed into the cement, which lowers infection risk and is one of the quiet advantages of cemented fixation.

Cemented vs. Cementless Knee Replacement

Bone cement is not used for every knee. Some patients do better with a cementless (press-fit) implant, and a few receive a hybrid of both. Here is how the options compare.

When cemented fixation is the right choice

• Softer or thinner bone. Cement grips well even when bone quality is reduced by osteoporosis or age, so it is a dependable choice for many older or less active patients.
• Immediate stability. The bond is solid the moment the cement cures, which supports same-day walking.
• A long track record. Cemented knees have decades of data behind them and routinely last 15 to 20 years or more.
• Infection protection. Antibiotics can be blended into the cement at the time of surgery.

When a cementless implant makes sense

• Strong, healthy bone. Cementless implants have a textured or porous surface that your own bone grows into over time, creating a biological bond.
• Younger or more active patients. A living bone-to-implant interface is appealing when an implant may need to last many decades.
• No cement to break down. Without cement, there is no cement layer to wear or loosen over the very long term.

What about hybrid fixation?

Some knees use a hybrid approach, with one component cemented and another press-fit. This lets me match the fixation to the bone quality on each side of the joint. It is one more way the plan is tailored to you rather than to a one-size-fits-all rule.

Are there any risks to bone cement?

Cemented knee replacement is very safe, and complications are uncommon. The concerns patients sometimes read about are worth understanding in context:

• Loosening over time. Like any building material, a cement bond can slowly weaken after many years of use. This is part of why a knee may eventually need revision, and it is a long-horizon consideration rather than an early one.
• Cement debris. In rare cases, small fragments can irritate nearby tissue. Careful technique and removing excess cement during surgery keep this risk low.
• Allergic reaction. True allergy to bone cement is very rare. I review your history and allergies before surgery as a standard precaution.

Most of these concerns are managed by good surgical technique and thoughtful patient selection, which is exactly why the cemented-versus-cementless decision matters. Precision helps either way. I use a muscle-sparing subvastus approach combined with Mako® robotic-assisted planning to position each component accurately. Better alignment means more even load transfer across the implant, which protects the fixation and the implant over time. You can read more about why a faster, lower-pain recovery is possible in my guide on subvastus knee replacement recovery.

The Bottom Line on Bone Cement for Knee Replacement

So, do I use glue? In a sense, yes, and that is good news. Bone cement for knee replacement is a proven, medical-grade material that has anchored millions of successful knee replacements for more than half a century. It is not a shortcut or a weak point. It is a carefully engineered material that locks your new joint in place, lets you walk the same day, and holds up for many years. For patients better suited to cementless fixation, modern press-fit implants offer an equally strong, biologically integrated alternative. The most important point is that the choice is individualized. There is no single best fixation for every knee. There is only the best fixation for your bone, your activity, and your goals. If you are weighing knee replacement and want a clear, honest answer about what will happen during your surgery, I would be glad to talk it through. Learn more about my background and approach, or schedule a consultation at the Bone and Joint Institute of Tennessee in Franklin, TN. No referral is required.

This article is for educational purposes only and is not a substitute for personalized medical advice. Always consult a qualified orthopaedic surgeon about your specific condition.

References

1. Vaishya R, Chauhan M, Vaish A. Bone cement. Journal of Clinical Orthopaedics and Trauma. 2013;4(4):157-163.
2. Charnley J. Anchorage of the femoral head prosthesis to the shaft of the femur. Journal of Bone and Joint Surgery (Br). 1960;42-B:28-30.
3. Tan ACK. The use of cement in revision total knee arthroplasty. Journal of Orthopaedics. 2021;23:97-99.
4. American Academy of Orthopaedic Surgeons. Total Knee Replacement. OrthoInfo.