Experimental Immobilization and Remobilization of Rat Knee Joints

Abstract

The knee joints of 39 adult rats were immobilized by internal fixation in the position of flexion in almost normal weight bearing, and re-mobilized at various intervals for 15 to 90 days. Proliferation of intracapsular tissue and formation of adhesions are the primary responses; to a limited degree, these changes are reversible. Irreversible changes occur in articular cartilage as follows matrix fibrillation, cleft formation and ulceration. After 30 days of rigid immobilization the joint changes that restrict motion are not reversible.