Unlike a monocentric knee with a fixed knee center, a polycentric knee can vary the instantaneous center of rotation (ICR) during flexion. According to Eqs 1 , 2 , the value of X b / Y b or X s / Y s determines how the knee center influences the user’s minimum required effort.

Prosthetic knees can be divided into Mechanical or Computerized. Mechanical knees can then be subdivided into single-axis and multiaxis/polycentric knees. All prosthetic knee require some sort of stability mechanism, this can be manual or a weight-activated locking system.

Feb 3, 2025 · Experimental results showed that the optimized polycentric hinge yields less relative motion and a lower chance of exoskeleton migration. The proposed method emphasizes the importance of minimizing relative motion rather than replicating the knee’s ICR and provides a systematic way to design and evaluate various knee hinge designs.

The monocentric mechanical joint is probably the simplest design of knee unit. It provides a basic hinge function allowing the knee to bend and extend. All monocentric knee units are highly dependent on prosthetic alignment and without additional functional mechanisms, are currently very limited in their area of application.

Dec 20, 2023 · This research proposes a novel design of a 4-bar polycentric knee with stance-phase knee flexion ability (4BSF), which can perform both stance and swing-phase knee flexion, like able-bodied...

Jul 18, 2016 · Polycentric knees for transfemoral prostheses have a variety of geometries, but a survey of literature shows that there are few ways of comparing their performance. Our objective was to present a method for performance comparison of polycentric knee geometries and design a new geometry.

Mar 28, 2019 · Computer-aided designs (CADs) and photographs of a novel prototype orthotic knee joint with two degrees of freedom. A: CAD showing the polycentric hinge (red arrow) and drawer joint (yellow arrow) in a neutral position. B: CAD showing the joint components in a flexed and rotated position in the sagittal and transverse planes, respectively.

Comparison between these two different knee hinges, Optimal Knee Hinge and the theoretical motion performed by a human knee reveals that a common monocentric hinge has a maximum misalignment of up to 27.2 mm; a polycentric hinge has a maximum misalignment of 23.9 mm.

In polycentric knee joints, the upper and lower parts of the knee joint are usually connected via a four-bar linkage mechanism. They rotate around an instantaneous center of rotation (ICR), which is dependent upon the knee flexion angle.

The literature review discussed four distinct knee joint designs: a single-axis joint, the Double-Hinge Gear Joint, the External Knee Joint Design Based on Normal Motion, and a joint with passive ICR translation.