Final Answer:
A joint that is extended beyond the zero position is said to be in hyperextension.
Step-by-step explanation:
Hyperextension refers to the extension of a joint beyond its normal or zero position. In anatomical terms, extension is the movement that increases the angle between two body parts. For example, straightening the elbow joint from a flexed position is extension. Hyperextension occurs when the joint is extended beyond its neutral or zero position. This is often observed in joints like the knee or elbow when they are moved backward beyond the straight or neutral position. While some degree of extension is normal and necessary for movement, hyperextension can lead to injuries, particularly if it goes beyond the joint's normal range of motion.