The elbow and the knee are examples of which joints?

• A. Hinge joints
• B. Ball and Socket joints
• C. Pivot joints
• D. Saddle joints

Answer: (A)

Movement is focused in a single plane, bending and straightening like a door on a hinge. Elbows and knees fit this pattern because the ends of the bones lock together along a single axis, allowing mainly flexion and extension. In the elbow, the ulna’s trochlear notch and the humerus’ trochlea create a simple, hinge-like contact that guides this one-direction movement. In the knee, the femoral condyles roll and glide over the convex tibial plateaus, providing primarily bending and straightening, with strong ligaments stabilizing the joint.

This is different from ball-and-socket joints, which permit movement in many directions and rotation (like the shoulder and hip); or pivot joints, which rotate around a single axis with a rotating bone around another. So the elbow and knee are hinge joints, reflecting their primary role in bending and straightening tasks.