Range of motion

Range of motion describes the extent of movement at a joint, such as the shoulder, expressed in terms of degrees. Range of motion varies by type of joint, as well as concerns such as the tendons, muscles, and ligaments. It is important in physical therapy and rehabilitation, such as following injury or surgery.

Range of motion can be described as both active and passive. Active range of motion describes an individual moving the joint through its range, while passive range of motion describes the extent to which another person, such as a doctor, is able to move the joint. Range of motion is a concern for many individuals, such as those with repetitive stress injury caused by work or recreational activities, such as throwing a ball.

Background

Kinetics is the study of forces on the body. The term dates to the mid-nineteenth century. Kinematics is the description of motion, and kinesiology is the study of body movement. These words all have their origin in the Greek kinein, meaning "to move."

Scientists have been interested in motion, and in particular human motion, for centuries. Early anatomical study often involved death rites, such as ancient Egyptian mummification methods. Ancient Greeks established the field of medical science and learned about the body through dissection and observation. For centuries, knowledge of anatomy and medicine relied on their texts.

Leonardo da Vinci, an artist and scholar of the Italian Renaissance, studied anatomy by dissecting humans and animals beginning in the 1480s. He drew bone and muscular structure, the heart and vascular system, and even a fetus still in the uterus of its deceased mother. Over the course of decades, he created more than 240 anatomical drawings and made copious notes. His detailed sketches reveal the mysteries of the mechanics of movement and are admired into the twenty-first century for their remarkable accuracy. Da Vinci was keenly aware of biomechanics, or the mechanical aspects of systems in humans and other creatures. He also used his information about bodies in his designs of theoretical machinery and inventions, such as flying machines.

During the sixteenth and seventeenth centuries, several scientists wrote important medical books that included details of human anatomy that were the basis of medical training for generations of doctors and researchers. Numerous scientific developments, such as the creation of the microscope during the seventeenth century, contributed to the wide scope of knowledge of the human body and its workings. Surgical advances from the eighteenth through twentieth centuries further increased medical knowledge. Henry Gray's Anatomy, Descriptive and Surgical was first published in 1858, and became the primary reference for human anatomy.

For early scholars, one difficulty in understanding movement was that the human eye could not see it well because animals in particular moved too quickly. The advent of photography helped researchers better understand movement. With this newly available knowledge, and detailed books on anatomy, surgeons turned to addressing a number of medical issues. Among these issues were repairing and treating joint damage and deterioration. In 1890s Germany, orthopedic surgeons used ivory to attempt to repair hip joints. Other efforts using various materials, including glass, followed in Europe and the United States. Many twentieth-century scientists were interested in biomechanics. Much of this interest was related to physical fitness and a focus on increasing athletic performance. The injuries sustained by troops during World War II (1939–1945) led to greater demand for medical advances to help individuals to walk and function well, again incorporating biomechanics into devising medical treatments.

Surgeons successfully used metal prostheses to repair joints during the 1950s. By the 2010s, more than seventy-five thousand joint replacement procedures were performed annually in Great Britain alone, and more than one million were performed in the United States each year.

The study of movement advanced to incorporate biochemistry, psychology, and other fields during the twentieth century, and became known as kinesiology. Technological advances, such as computer-aided automated motion capture, help researchers better understand bone and muscle movement. This insight has provided information about joints and range of motion of various body parts as well.

Overview

Individuals with limited active range of motion may have difficulty performing everyday tasks. Limitations may also affect athletes and may lead to injury. Range of motion is expressed in terms of degree and is measured using a goniometer. For example, the wrist joint, when the lower arm is held horizontally and the hand is held straight with palm down, is at 0 degrees, or a neutral position. Flexed upward fully, or hyperextended, it should reach up to 60 degrees, and the downward flexion-extension may also reach 60 degrees. The joint cannot flex further in either direction. The wrist also moves right and left, with a radial flexion (on the thumb side of the hand) of up to 20 degrees, and ulnar flexion (on the pinky side) of up to 30 degrees.

Flexion may be measured for both active and passive range of motion. Passive range of motion is relevant primarily for those with long-term concerns, such as individuals using wheelchairs. While passive range of motion may not affect one's ability to perform needed tasks, having joints manipulated by a medical professional can help reduce pain and maintain range of motion. Passive range of motion is often important to physical therapy after an injury.

Physical therapy of a joint includes an assessment of range of motion. A professional evaluates and measures the movements of the affected area, commonly the ankles, elbows, fingers, hips, knees, shoulders, and wrists. This may include measuring an injured limb's movement and comparing it to the uninjured limb—for example, a right shoulder injury may cause reduced range of motion, and the therapist also measures and records the range of the left shoulder. The physical therapist determines if motion is limited and what is hindering movement, and formulates a therapy plan including motion exercises. These may include passive range of motion exercises, in which the physical therapist moves the limb or body part. Passive range of motion exercises are commonly used to prevent stiffness in a joint when a patient is immobilized, such as because of paralysis or illness. Physical therapists may also aid patients with active-assistive range of motion exercises, in which the therapist helps a patient with pain or limited strength to fully extend a limb. A third type of exercise, active range of motion exercise, is performed by the patient without assistance. The physical therapist verbally prompts the patient in correctly completing the movements. After therapy, therapists may measure range of motion again to compare the degree of movement and assess the impact of treatment.

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