Physiology and therapeutic value of passive joint motion.

Despite the long history of therapeutic experience with different types and amounts of passive joint motion, its effects and the principles of its use remain controversial. Through empiric success, a spectrum of passive motion has evolved for various clinical purposes, including joint diagnosis; correction of joint deformities; mobilization of stiff joints; stimulation of joint healing; neuromuscular re-education; and prevention of immobilization complications (e.g., contracture formation, connective tissue atrophy, relative healing inhibition, and associated stasis abnormalities). However, the potential abuses of passive motion (e.g., causing additional tissue trauma, mobilizing unprotected joints, and stretching the wrong joints or tissues) have created serious doubts as to the value of this therapy and raised important questions concerning the lack of proper definition (e.g., force, direction, speed, and duration) and the unknown margins of safety. Clinical and experimental evidence supports the probable effectiveness of passive joint motion on joint and tissue levels, but without a better quantitative understanding of the mechanisms of action, dose-responsiveness, specific tissue effects, and, most important, their controls. Thus, passive motion will continue to be used suboptimally with inconsistent results. When these clinical and research deficiencies are corrected, passive motion will attain its proper place as a powerful and reliable orthopedic tool.