The Ottobock C-Leg is a microprocessor-controlled knee prosthesis. Introduced to the world in 1997, the C-Leg was the first prosthesis system to intelligently control and adapt to an individual’s gait. The C-Leg uses hydraulic cylinders to control knee flexing. Sensors send information to the microprocessor controlling how much resistance should be provided by the cylinders. The microprocessor receives information from the sensors 50 times a second, effectively adjusting itself in real-time. The microprocessor can also secure the stance phase. The result is a system that recognizes which phase of gait the user is in and reacts accordingly. This keeps the knee of the user stable when weight is put on it but allows free-swinging as the user steps through. C-Leg technology offers the advantages of permanent stance phase control, the ability to weight the prosthesis during flexion, dynamic alignment, less energy expenditure while walking, and relief for the sound side and the rest of the body.