The study, measurement, and evaluation of the ranges of joint motion is a complex and relatively sophisticated science. Measuring techniques have not been completely perfected and some yet remain to be devised. Research with respect to certain aspects of the dynamics involved, particularly in terms of the interaction of two or more joints or muscles, is still in its early stages. The data available are scarce, and information specifically related to large samplings of the civilian population practically nonexistent. Table 9 includes what information is available concerning ranges of joint motion relative to the neck, spine, shoulder, elbow, hip, knee, wrist, fingers, ankle, and foot. Most of the data, however, are based on a military population and are concerned primarily with the simple movement of a single joint and not with the effect of one upon the other. Proper allowances for clothing and shoes should be added to all data.
Human Factors Engineering, 3d ed., AFSC Design Handbook 1-3, January 1977, Department of the Air Force, Headquarters Air Force Systems Command, Andrews AFB, DC 20334, pp. 16–17.
Flexion: bending or decreasing the angle between the parts of the body. Supplementing the more commonly measured arm and leg flexions, several kinds of flexion have been identified to meet special descriptive needs. These are trunk lateral flexion in which the trunk segments move so as to decrease the angle between them and the right thigh; radial flexion, which refers to the movement of the thumb side of the hand toward the radial side of the forearm segments; and ulnar flexion, which refers to the opposite side of the hand’s movement toward the ulnar side of the forearm segment.
Extension: straightening or increasing the angle between the parts of the body. It is generally defined as the return from flexion. When a joint is extended beyond the normal range of its movement, the movement becomes known as “hyperextension.”
Abduction: movement of a body segment away from the midline of the body or body part to which it is attached.
Adduction: movement of a body segment or segment combination toward the midline of the body or body part to which it is attached.
Medial rotation: turning toward the midline of the body.
Lateral rotation: turning away from the midline of the body.
Pronation: rotating the forearm so that the palm faces downward.
Supination: rotating the forearm so that the palm faces upward.
Eversion: rotation of the foot which lifts its lateral border to turn the sole or plantar surface outward.
Inversion: lifting the medial border of the foot to turn the sole inward.
