Knees and elbows are categorized as what type of joints?

Knees and elbows are classified as hinge joints, which is the correct answer. Hinge joints are characterized by their ability to allow movement primarily in one plane, functioning similarly to the way a door opens and closes. This design enables flexion and extension movements, which are the key actions performed at the knee and elbow.

In the case of the knee, this joint allows for bending and straightening, crucial for activities like walking, running, and jumping. Similarly, the elbow facilitates movement between the forearm and upper arm by enabling bending and extending of the arm.

Other joint types, such as ball-and-socket joints, allow for a wide range of motion in multiple directions (like the shoulder), while condyloid joints provide more limited movement in two planes (like the wrist). Pivot joints permit rotational movement (like the neck). Therefore, the unique structure and function of hinge joints specifically align with the movements performed by the knees and elbows, making this classification accurate.