## Introduction
The stability of a Total Knee Arthroplasty (TKA) depends on the balance between the metal implants and the patient’s own ligaments. If the ligaments are weak or missing (**Ligament Laxity**), the surgeon must use the polyethylene insert to provide the missing stability.
## 1. Cruciate Retaining (CR) – Non-Constrained
* **Requirement:** An intact and strong Posterior Cruciate Ligament (PCL).
* **Mechanism:** The insert is relatively flat; the PCL does the work of stabilizing the knee during flexion.
## 2. Posterior Stabilized (PS) – Semi-Constrained
* **Scenario:** When the PCL is absent or weak.
* **Mechanism:** The insert features a central “post” that interacts with a “cam” on the femoral component, preventing the femur from sliding too far forward.
## 3. Constrained Condylar Knee (CCK) – Highly Constrained
* **Scenario:** When the collateral ligaments (MCL or LCL) are incompetent or when there is severe bone loss.
* **Mechanism:** A much taller and wider central post that provides both AP and varus/valgus stability.
## The Ortholyx “One-System” Philosophy
The Ortholyx TKA platform is designed for **Intraoperative Flexibility**.
* Surgeons can use the same femoral and tibial components and decide on the level of constraint (CR, PS, or CCK) based on the ligament tension they feel during the surgery.
## Conclusion
Constraint is a trade-off: more stability means more stress on the bone-implant interface. By offering a full range of insert options, Ortholyx allows surgeons to choose the “minimum necessary constraint” needed to achieve a stable, long-lasting knee.