After above-knee amputation, the prosthetic knee joints used are basically considered in two groups: mechanical knees and microprocessor knees. Understanding the difference between the two groups can provide guidance in choosing a solution suited to the person's needs. The appropriate type of prosthesis is determined in line with the specialist physician's assessment and the measurements and trials carried out by the prosthetist.
Mechanical and Microprocessor Knees
Mechanical knee joints use locking, friction or hydraulic/pneumatic fluid systems and generally rely on body weight for stance control. Microprocessor knees, on the other hand, continuously detect walking by means of sensors and software and adjust fluid-based resistance step by step. In this way, walking at different speeds, descending ramps and stairs, and standing may become more controlled.
The Two Phases of Gait
All prosthetic knee joints are designed to imitate the two phases of the natural walking pattern:
- Stance phase: The phase in which the foot is in contact with the ground and body weight is carried.
- Swing phase: The phase in which the leg moves freely forward.
In microprocessor knees, sensor data are evaluated continuously throughout these two phases; resistance is adapted to the movement at that moment.
Safety Features
Stumble detection systems found in some microprocessor knees can help support the knee by detecting moments when balance is lost, and aim to reduce the risk of falling. Standing support features aim to allow the person to stand comfortably with fewer compensatory movements while waiting on their feet. The suitability of these features for a person varies according to the amputation level, the condition of the residual limb and their general physical condition.
Water and Dust Resistance
The resistance of devices to water and dust is expressed by the ingress protection (IP) rating. While some models are protected only against rain and splashes, some models with a higher protection class are resistant to the level of being submersible in water. Because the conditions of use depend on the technical specifications of the device, it is important to follow the manufacturer's information and the prosthetist's guidance.
Activity Modes
In addition to the basic walking mode, some microprocessor knees offer additional modes that can be set for different activities. These settings are programmed individually by the prosthetist; the user can switch between these modes in daily life.
The Assessment Process
The suitability of a prosthetic knee is an individual decision. It is recommended to work with a physiotherapist to strengthen the muscles that will support a microprocessor knee, and with a prosthetist to determine and trial the solution suited to the person's needs. All interventions are carried out in line with the specialist physician's prescription and medical report.
This content is for informational purposes only; you should consult your physician for diagnosis and treatment.
