More than half a million Stryker Scorpio Knee Systems have been implanted worldwide during the past decade. The Scorpio Knee System is popular among physicians and patients because it maintains a constant center of rotation throughout the range of motion, providing uniform ligament tension during the transition from full extension to deep flexion. By preserving ligament isometry the Scorpio Single Axis Total Knee System helps address mid-flexion instability, which is a common concern in multiple axis knee designs.