Artificial joints for orthoses, exoskeletons or prostheses have an upper part with an upper connection part and a lower part with a lower connection part, which are articulatedly connected to one another. In general, in the case of artificial knee joints, receptacles for a thigh stump or a thigh rail are arranged on the upper connection part, whereas a lower leg tube or a lower leg rail with a prosthetic foot or a foot part are arranged on the lower connection part. In the case of a lower leg still being present, the upper part of a prosthesis is arranged on a lower leg socket, the prosthetic foot is fastened to the lower part, and in the case of orthoses, the respective components are fastened to the associated limbs. In the simplest case, the upper part and the lower part are connected pivotably to one another by means of a uniaxial joint.
To be able to satisfy or support different requirements during the different phases of a step or during other movements or actions in a way that is as natural as possible, a resistance device is often provided which provides flexion resistance and extension resistance. The flexion resistance is used for setting how easily the lower part can be pivoted in relation to the upper part when a force is applied. In the case of a knee joint, the extension resistance brakes the forward movement of the lower part and forms, inter alia, an extension limit stop, and the flexion resistance prevents undesired flexion and limits the maximum flexion in the swing phase.
DE 10 2008 008 284 A1 has disclosed an orthopedic knee joint with an upper part and with a lower part arranged pivotably thereon, which lower part is assigned multiple sensors, for example a flexion angle sensor, an acceleration sensor, an inclination sensor and/or a force sensor. The position of the extension stop is determined in a manner dependent on the sensor data.
DE 10 2006 021 802 A1 describes control of a passive prosthetic knee joint with adjustable damping in a flexion direction for adaptation of a prosthesis device with top-side connection means and with a connecting element to an artificial foot. The adaptation is made to climbing stairs, wherein a low-moment lifting of the prosthetic foot is detected, and the flexion damping is, in a lifting phase, lowered to below a level suitable for walking on a level surface. The flexion damping may be increased in a manner dependent on the change in the knee angle and in a manner dependent on the axial force acting on the lower leg.
DE 10 2009 052 887 A1 describes, inter alia, a method for controlling an orthotic or prosthetic joint with a resistance device and with sensors, wherein items of state information are provided by means of sensors during the use of the joint. The sensors detect moments or forces, wherein the sensor data of at least two of the determined variables are linked to one another by means of a mathematical operation, and in this way an auxiliary variable is calculated which is used as a basis for the control of the flexion and/or extension resistance.
According to the prior art, for the control of the change in the damping behavior, the sensor data are evaluated quantitatively, that is to say, in general, certain threshold values are predefined, in the case of the attainment or non-attainment of which the actuator is activated or deactivated, such that the resistance device provides an increased or reduced flexion or extension resistance.
Patients may use prostheses, exoskeletons or orthoses in various environments. They may walk down stairs, walk down ramps or walk on a level surface at various speeds. Furthermore, loads may be carried, which likewise has an effect on the behavior of the prosthesis or orthosis. In particular after the end of the swing phase, that is to say after the setting-down of the aided leg, when the body weight is shifted onto the aided leg, there is often a requirement for increased safety for the patient. Excessively high initial flexion damping, that is to say damping which counteracts flexion of the artificial knee joint, would however lead to a shock load in the hip joint, which would result in a reduction in wearing comfort and acceptance of the prosthesis or orthosis.
Modern computer-controlled damping devices are capable of adapting the resistance to flexion or extension in a very precise and rapid manner. Limiting factors are the accuracy of the determined or detected data, the complexity of the information to be processed, the reliability of the detection of the movement respectively being performed, and the outlay in terms of construction.