Muscle tension and joint mobility.

Even when the muscles surrounding a joint are inactive, they still exert a damping effect on joint mobility, because of the passive elastic tension exerted by the stretched muscle fibres and their connective tissue (Clemmesen, 1951). For example, if the forearm muscles are allowed to relax and the forearm is then shaken violently, the hand will swing loosely at the wrist; however, if the experiment is repeated post mortem after all the tendons that cross the wrist have been severed, it is obvious that wrist mobility is considerably increased. Johns and Wright (1962) have estimated the effect of passive elastic tension in muscles by comparing the freedom of movement exhibited by an anaesthetized cat's wrist before and after dividing the forearm tendons. In the present study, measurements have been made of finger mobility in man after the muscles and tendons have been rendered ineffectual.