Which structures contribute to the stability of the knee joint?

The stability of the knee joint is primarily ensured by various ligaments and structures that provide support and restrict excessive movement. The anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) are crucial for stabilizing the knee in the anterior-posterior direction; they prevent hyperextension and control sliding movements of the tibia relative to the femur. Meanwhile, the medial collateral ligament (MCL) and lateral collateral ligament (LCL) contribute to the stability of the knee by preventing excessive side-to-side movement, thus protecting against varus and valgus stresses.

This combination of ligaments works synergistically to stabilize the knee during weight-bearing activities and dynamic movements, making them essential for knee joint integrity, particularly during activities involving twisting or pivoting. Other structures such as the meniscus, while important for shock absorption and joint congruence, do not directly contribute to the ligamentous stability of the knee in the same way. The muscles mentioned in other answer choices, while they assist in movement and provide dynamic stabilization through contraction, do not serve as passive stabilizers like the ligaments do. Therefore, the correct answer highlights the key ligamentous structures that are primarily responsible for maintaining the stability of the knee joint.