Date of Award

Summer 1987

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Biomedical Engineering


Neuro-muscular control about the knee joint in normal and spastic individuals is the topic of interest in this dissertation. Spasticity is a neuro-muscular disorder of muscle tone due to injuries of the upper motor neurons. It also indicates that the muscle-stretch reflex has become isolated from its supraspinal inhibitory-modulation system. The neuro-muscular control system about the knee joint has been modeled and represented schematically by an information-flow diagram. A quantitative analysis is then performed to fit a mathematical model for the blocks constituting this information-flow diagram. Finally, a block diagram containing only mathematical symbols is built to represent the model. In order to better understand the responses of neuro-muscular control system about knee joint, and the mechanism of lower limb spasticity, a testing device has been designed and built which passively moves the lower limb. The design of the testing device is based upon a kinematic model and analysis of the neuro-muscular/ skeletal components of the lower leg. The system is capable of performing three types of tests: ramp test, dynamic test, and impulse test. The extension/flexion torque about the knee joint, the abduction/adduction torque, the lower leg angular position, and the processed surface EMG's from quadriceps and hamstrings muscle are the signals of interest. Data are acquired from the torque reaction sensor, self-mounted strain gage, rotational potentiometer, and EMG amplifiers by a 10 bit A/D converter, with a data sampling rate of 200Hz. The intrinsic muscular stiffness and visco-elastic damping coefficient of passive model were calculated and normalized to compare the results from both normal and spastic groups. Also compared were the total energy and normalized energy of extension and flexion for both groups. The extension/flexion torques were plotted against the angular velocity to examine the threshold velocity at eight different positions of the lower leg for ten normal subjects and eight spastic subjects. The results were found to be consistent, highly reproducible, and in agreement with previously reported physiological phenomena. Performance of the device attests to the satisfaction of the design objectives and demonstrates the model's usefulness for applications in various physiological investigations performed about the knee.



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