Range of motion (ROM)

Range of motion is the full extent of movement a joint can perform in a given direction, measured in degrees and used to track joint health and recovery.

Each joint has a normal range for each movement, such as flexion, extension, rotation, abduction and adduction, set by the shape of the bones and the length and elasticity of surrounding ligaments, capsule and muscles. Active range of motion is what a person or animal can achieve by their own muscle effort; passive range is what an examiner can move the joint through. A gap between the two suggests weakness or pain rather than mechanical restriction.

Clinicians measure range of motion with a goniometer, a hinged protractor placed along the limb, or with digital inclinometers and motion capture in research. Reduced range accompanies osteoarthritis, injury, immobilization, swelling and muscle tightness, and it is a standard outcome in physical therapy and in veterinary orthopedics, where it is measured in dogs with hip and elbow disease. Range of motion is a measurement, not a condition, and it is reported alongside pain scores and function in clinical studies.