Today, we(shijiazhaung aosuo ) have a lot of prosthetic joints can be used. This time, we are not talking about the function and characteristics of each knee unit, but try to classify and explain the thoughts behind different types of knees.

Single Axis prosthetic joint

This knee is the simplest design. It provides a basic hinge function that allows the knee to bend and stretch. All this kind knee joint are highly dependent on prosthetic alignment and have no additional functional mechanisms and are currently very limited in their application areas. For safety reasons, this kind of knee is usually combined with the mechanical manual start lock. In this case, the user uses a fixed straight prosthesis to walk and unlock it to sit down.

The photo above demonstrates a prosthetic joint with a simple mechanical lock.

To add more function to this base design, a spring can be added to provide assisted extension (straightening) of the knee joint. This can be considered a safer device as the user will have a lower risk of standing on a bent unstable knee.

But what happens if, even with the spring, the user can stand on this knee when it is slightly bent? The knee will immediately collapse underneath them. To avoid this situation, a mechanical friction break can be added which will prevent a loaded knee from bending. However, it is important to note that a friction brake will only work when the knee is bent at a very slight angle. Because the break is a mechanical friction device that utilises the contact of two surfaces, it will wear out overtime and require a service to maintain proper functional sensitivity.

The photo above demonstrates a knee joint with breaks and a spring assist.

To further improve the functionality of a single axis knee joint, a pneumatic system can be installed. Pneumatic systems are designed to control the knee joint’s flexion and extension speed during the swing phase of gait (when the prosthesis is off the ground during walking). This system allows the prosthetist to adjust the knee to the users general walking pace. The result is a smoother movement of the prosthesis. Pneumatic systems usually consist of a cylinder and piston with manually adjustable valves. As the knee bends, the piston in the cylinder compresses air which escapes past it through the valves. By adjusting the aperture of these valves, the prosthetist adjusts how easy it is to bend and extend the knee.

The photo above demonstrates a monocentric knee joint with a pneumatic system and friction breaks.

What’s more,With the development of science and technology, prosthetic knee will be more and more close to the real knee, will be more comfortable, suitable for people's daily life, exercise.

We(shijiazhuang aoso) will also try to make your life full of infinite possibilities.