Glossary
Cemented vs uncemented implants
Quick answer
Cemented implants are fixed to bone with a fast-setting acrylic bone cement, giving immediate stability, while uncemented implants have a porous surface that bone grows into over weeks. Both work well in knee replacement, says Doha knee surgeon Dr. Pablo Gelber, and the choice depends on bone quality and the implant.
What the terms mean
Bone cement, polymethylmethacrylate, is mixed in theatre and acts as a grout between implant and bone, hardening within minutes. Cemented fixation has been used in knee replacement for decades and remains the most common method worldwide.
Uncemented, or press-fit, implants are made slightly tight and coated with a rough or porous metal surface. Living bone grows onto and into that surface, creating biological fixation. Some knees use a hybrid, with one part cemented and another not.
Why it matters for patients
Cemented fixation gives full stability on the day of surgery and suits most bone types, including softer bone in older patients. Antibiotic-loaded cement can also be used.
Uncemented fixation avoids cement and may offer long-lasting fixation in younger, active patients with good bone, although early discomfort can be a little greater while bone grows in. Long-term registry results for both are good.
How the choice is made
Your surgeon weighs bone quality, age, activity, the specific implant system and their own experience. Osteoporosis, for example, usually favours cement. In practice, weight-bearing and rehabilitation start early with either method.
Frequently asked questions
Can I walk straight away with an uncemented knee?
In most cases, yes. Uncemented knee implants are designed for immediate weight-bearing as tolerated, and rehabilitation usually follows the same early pattern.
Does cement wear out?
Cement can loosen over many years in some knees, as can bone ingrowth. Loosening is uncommon and is one of the things checked on follow-up X-rays.
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