Final answer:
A goniometer is used to assess joint flexibility by measuring the range of motion, indicating the flexibility of the muscles and ligaments around the joint.
Step-by-step explanation:
The device frequently used to assess flexibility at a joint is the goniometer. A goniometer is an instrument that measures the range of motion at a joint and is commonly used by physical therapists, athletic trainers, and other health professionals. It consists of two arms that can pivot around a h_inge to measure the angle of the joint flexion or extension. To determine flexibility, one arm of the goniometer is aligned with the body part that remains stationary during the movement, and the other with the part that moves. This helps in obtaining an objective measurement of how far the joint can move, which is an indication of the flexibility of the muscles and ligaments around it.