It has long been known that a passive movement, (i.e. movement of a joint, operated by someone else) of certain injured joint muscles, can be a relatively painless way to encourage a joint and the muscles of that joint to become more mobile. If performed by a qualified professional in a correct and gentle way, after first loosening the surrounding tissues by massage, can help restore the full range of movement to the area faster and easier than some other forms of treatment.
As the relaxed muscles are slowly and gently eased through the natural range of movement certain things are brought into play. The muscle begins to stretch the fibres that have been holding together trying to perform a protective spasm to stop the joint from further injury. The muscle begins to take on more nutrition and expel the toxins and waste products that have been building up because of the fibre's spasm.
The tendons are then able to move and regain their mobility and the ligaments of the joint can take on the job of allowing the joint to move again and stop any calcification building up around them. It also allows the body to make synovial fluid (in synovial joints) to "lubricate" the joint as this fluid may be lost because of the injury.