Changes in biomechanical properties of tendons and ligaments from joint disuse.

OBJECTIVE: The purpose of this paper is to review changes in the biomechanical properties of tendons and ligaments from joint disuse.
METHOD: We have reviewed 37 experimental studies on joint disuse, which have been carried out with various models of disuse and with various animals.
RESULTS: Immobilization of joints has most commonly been used as a model of disuse. Immobilization of the joint deteriorates the mechanical properties of tendons and ligaments, and reduces their cross-sectional area, although there are some differences in the speed of deterioration among tissues. Remobilization returns the mechanical properties once reduced by immobilization to nearly normal quickly, although the structural properties of the bone-ligament-bone complex continue to lag behind those of the controls. Stress deprivation has been regarded as an essential causative factor in joint disuse. Even if joint motion is allowed, stress deprivation rapidly reduces the mechanical properties of the tendon and ligament tissues, and increases the cross-sectional area of them. These effects appear time- and dose-dependent. Restressing increases the mechanical properties once reduced by stress deprivation, although it takes much time to completely recover them. The reduction of the ultimate stress may be explained by the reduction of the total area of collagen fibrils in tendon cross-section and the increase of thin and immature fibrils.