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Mechanism of thixotropic behavior at relaxed joints in the rat | JoVE Visualize

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Mechanism of thixotropic behavior at relaxed joints in the rat

Journal of Applied Physiology (Bethesda, Md. : 1985)|April 1, 1987

View abstract on PubMed

Summary

Joints exhibit thixotropy, a phenomenon where stiffness temporarily increases after a perturbation. This study reveals that both joint structures and muscle properties contribute to this adaptable stiffness in rat ankle joints.

Area of Science:

Biomechanics
Physiology

Background:

Thixotropy, a time-dependent decrease in viscosity under stress, is observed in human joints.
Relaxed joints exhibit transient increases in stiffness following perturbations, reverting to a stiffer state after inactivity.

Purpose of the Study:

To investigate the underlying mechanisms of thixotropic behavior in relaxed rat ankle joints.
To determine the relative contributions of joint structures and muscles to joint thixotropy.

Main Methods:

Experiments were conducted on intact, blood-perfused soleus muscle, isolated soleus muscle, and isolated ankle joint preparations in anesthetized rats.
Sinusoidal torque was applied to assess steady-state displacement response and the effect of transient perturbations.
Short-range stiffness properties of relaxed soleus muscles were analyzed.

Main Results:

Thixotropic behavior was present in all tested preparations (intact, isolated muscle, isolated joint).
The joint's contribution to thixotropy was comparable to, and sometimes greater than, the muscle's contribution.
Short-range muscle stiffness exhibited properties similar to thixotropy in terms of range, modulus, and recovery time.

Conclusions:

Thixotropic behavior in relaxed joints is a result of contributions from both joint structures and the short-range stiffness of muscles acting across the joint.
This adaptable stiffness mechanism may play a significant role in joint stability and function.

Mechanical Engineering

Mechanism Of Thixotropic Behavior At Relaxed Joints In The Rat