Which bone articulates with the knee and is the medial bone of the lower leg?

• A. Fibula
• B. Radius
• C. Ulna
• D. Tibia

Answer: (D)

The key idea is which bone forms the main knee joint and lies on the medial side of the lower leg. The knee primarily involves the femur above and the tibia below, with the tibia bearing most of the body's weight. Because it’s the main weight-bearing bone and sits medially, it articulates with the femur to form the knee joint. The fibula runs along the lateral side and doesn’t form the knee joint with the femur, though it provides muscle attachment and ankle stability. The radius and ulna are forearm bones, not related to the knee. So the bone that articulates with the knee and is the medial bone of the lower leg is the tibia.