Range of Motion

Active and Passive Range of Motion

Active range of motion, also abbreviated AROM, is defined as the arc of motion achieved through voluntary movement produced by an individual. AROM is produced by contractions of specific muscles that cross the joint, causing an angular motion to occur. Successful performance of full AROM depends on multiple factors. These include, but are not limited to, the following: an intact and normal function of the neuromuscular unit, intact muscle and tendon transcending the joint, normal strength, normal joint congruency and anatomy, and absence of soft tissue restriction.

Passive range of motion, commonly referred to as PROM, is defined as the arc of motion achieved through the assistance of external forces, without active assistance from the individual. PROM occurs only with complete lack of voluntary assistance from any muscle that crosses the joint. An individual receiving PROM would completely relax and play no active role in producing the movement. The achievement of full PROM depends on normal joint congruency and anatomy, and normal extensibility of the joint's surrounding soft tissue structures.

Osteokinematic and Arthrokinematic Movement

A joint or body segment moves through an ROM in any 1 or more of the 3 cardinal planes of motion in space: (1) sagittal, (2) frontal, and (3) transverse. Every joint in the body has a specific ROM in each plane of motion depending on the joint's structure. Understanding the ROM available at a given joint depends on understanding both the osteokinematic and the arthrokinematic movements occurring at the joint.

Osteokinematics is the study of the movement of bones relative to the 3 cardinal planes of motion of the body. The osteokinematic movement of a joint is measured and recorded as a joint's ROM. This can be measured as AROM or PROM depending on the methodology used. Each plane of motion, or independent movement allowed at a joint, is referred to as a joint's degree of freedom. Thus, a joint can have up to 3 degrees of freedom, depending on the joint's structure. When a health care clinician measures the ROM, that person is measuring the osteokinematic motion at a specific joint and in a specific plane of motion.

Arthrokinematics is the study of the motion occurring between the articular surfaces of a joint. [Page 966]Joint ROM depends on the normal arthrokinematic function in the joint being measured. Arthrokinematic motion is determined indirectly through observation of a joint's movement, with knowledge of the shapes of the articulating surfaces. Most joint surfaces are curved, with one end of a joint taking on a concave shape and the other taking on a convex shape. These shapes of articulating surfaces of a joint serve to improve joint congruency, increase surface area to dissipate contact forces, and guide osteokinematic movement.

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