A FEM-based force-strain transfer matrix technique for estimating forces in a knee brace

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Biomedical Engineering

First Committee Member

Shihab Asfour - Committee Chair

Second Committee Member

Ahmad Namini - Committee Member


The control of translations and rotations of the knee outside the normal range of motion, in addition to the loading across the joint for selected activities, are the most critical performance criteria required in the design of the knee brace. Information about loading in the knee brace as well as the knee joint may be of great benefit to the design and function of the knee orthoses and to the recognition of activities which challenge the knee stability. Measuring the forces and moments in the brace can provide a means to estimate the loads in the knee joint. Few studies have attempted to evaluate the performance of the knee braces in the type of activities for which they are intended, high performance in the field. The first prototype of an instrumented knee brace for strain measurements in the field without any umbilical cord has been built at the University of Miami. Soon, it became evident that without a mechanism to estimate the actual loads being transmitted by the brace from these strain measurements, it is difficult to evaluate exactly what the brace is doing mechanically.The main objective of this dissertation was to develop a methodology to estimate mechanical forces and moments in the knee brace members from strain gauge readings with the help of a finite element model. A force-strain transfer matrix technique was developed to achieve this goal. The reliability of the loads estimated with this technique will be determined by the quality of the strain readings and the boundary conditions assumed in the finite element model.The methodology developed is a powerful tool in the understanding of the mechanical behavior of the knee braces in the conditions that they were design for, high performance activities in the field. Even more, the technique presented can be used for other types of braces in other important joints of the musculoskeletal system, as long as the brace can be instrumented and a suitable finite element model created.


Health Sciences, Rehabilitation and Therapy; Engineering, Biomedical

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