A knee joint is well known in the art which is one of the strongest and most important joints in the human body. It allows the lower leg to move relative to the thigh while supporting the body's weight. Movements at the knee joint are essential to many everyday activities, including walking, running, sitting and standing.
The issues due to osteoarthritis and other knee diseases such as rheumatoid arthritis, psoriatic arthritis, etc's are solved by knee replacement which is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability.
In major issues, the artificial prosthetic knee joint imitates the functions of the human knee. Prosthetic knee joints use various techniques to allow the leg to be bent and to allow the lower leg to be swung forward after the bending movement. In knee joints, the knee joint angle (angle between the thigh and the shank) is one of the important parameters for determining the proper functioning of the knee.
The existing artificial prosthetic knee joint is classified into two types: single axis and multi axes knee joint. In a single axis knee joint, which is also called as a fixed knee, the locking mechanism is controlled by the amputee. In this design, knee stability during weight-bearing is achieved by positioning the knee axis in such a way, relative to the body-weight action line, that the knee can be extended. In addition, a movement from active hip-extension muscles is required during the weight-bearing phase of the walking cycle. This means that the amputee must walk during weight-bearing over a fully extended knee, which is physiologically abnormal and contributes to the unnatural appearing gait of the “above-knee” amputees.
In case of multi axes knee joint, the locking of the knee is controlled by self weight of the patient, which also acts as a brake to prevent the bending of the knee. The multi axes knee joint is composed of multi-links mostly four-bar link used for knee mechanism which has better functionality when compared to a single-axis knee joint, which is also called as a polycentric knee joint.
In addition, these knee joints generally have been complicated in structure, including complex spring and/or hydraulic mechanisms to achieve the desired performance, which has resulted in high cost, heavy weight, and inadequate reliability.
Moreover, still now there is no low cost passive polycentric knee joint with superior functionality. The gait analysis along with constrains of ICR, optimum link length, flexion angle, transmission angle and voluntary control zone are not well defined. Further, the existing knee joints are found to be heavy weight and expensive due to the presence of actuators in the active knee joint and there are many amputees, who are not able to afford the knee joint from under developed and developing countries. The extension bias in the passive polymer knee joint is not achieved fully to take care of the buckling of the knee joint during swing phase.
Many trails with resilience device springs came into picture in passive knee joint to achieve the extension bias. But, the normal walking gait cycle is still a concern. In addition to this, controlling of different phases such as stance phase and swing phase is still a major concern in knee joint.
Therefore there is a need in the art with the polymeric composite or nanocomposites based passive polycentric knee joint to solve the above mentioned limitations with affordable price.