Total Knee Arthroplasty Bearing Options


The optimal tibial bearing design in total knee arthroplasty (TKA) remains controversial. Options include posterior stabilized (PS), cruciate retaining (CR), condylar stabilized (CS), and ultracongruent (UC) inserts. Recent studies help clarify the relative merits of each implant.

PS Implants

The PS design substitutes for posterior cruciate ligament (PCL) function with a tibial post and femoral cam. PS TKA facilitates ligament balancing but requires additional bone resection. Drawbacks include patellar complications and mechanical noises.

CR Implants

CR TKA preserves the PCL for proprioception and kinematics. However, the PCL is often degenerated and nonfunctional. CR designs are technically more demanding to balance.

CS Implants

CS inserts lack a posterior lip, providing intrinsic stability without a PS cam mechanism. One randomized trial found no clinical differences between PS and CS devices.

UC Implants

UC inserts have high anterior lip heights for anteroposterior stability. Proposed benefits over PS designs include decreased noise, blood loss, and bone resection. Several studies show excellent function and kinematics.

Comparative Outcomes

Recent randomized and registry studies demonstrate equivalent outcomes between modern PS, CR, CS, and UC implants in terms of function, pain, and flexion. UC inserts show a trend toward earlier recovery and less pain. Survivorship exceeds 90% at 15-20 years for all designs.


While bearing options rely on different mechanisms for stability, improved materials and congruency minimize clinical differences. Surgeon experience and technical factors drive implant selection. Further study on kinematics and long-term wear is warranted.

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© 2023 Dr. Robert Afra – San Diego Orthopedic Surgery Shoulder – Knee – Elbow