Goniometry

Goniometry is the measurement of a joint's range of motion (ROM) using a goniometer, a protractor-like instrument that quantifies the angle formed by adjacent body segments around a joint axis. It is widely used in physical therapy, orthopedics, sports medicine, and rehabilitation to document mobility, track changes, and guide treatment.

The universal goniometer is the most common tool, featuring a stationary arm, a movable arm, and an axis that aligns with the joint center. Alternative devices include inclinometer-based systems, digital goniometers, finger goniometers, and smartphone apps. Proper landmarks and patient positioning are essential for valid readings.

Measurement procedures typically involve identifying bony landmarks, aligning the stationary arm with the proximal segment, the movable arm with the distal segment, and placing the axis at the joint center. Measurements can be taken actively by the patient or passively by the examiner, and are usually repeated to improve reliability.

Applications include establishing a baseline ROM, monitoring progress during rehabilitation, informing surgical decisions, and researching joint function. Normative values vary by joint, age, and sex; clinicians compare patient ROM to published data or control values.

Reliability depends on examiner skill, landmark palpation, and consistency of positioning. Common limitations include inter- and intra-tester variability, soft tissue and pain limiting movement, and instrument error. Standardized protocols and training help reduce measurement error.

Typical ranges (approximate) include shoulder flexion 0–180 degrees, shoulder abduction 0–180, elbow flexion 0–150, knee flexion 0–135, and ankle dorsiflexion 0–20. Normative data should be referenced per joint and population.