What structure is responsible for the "locking" mechanism of the knee during standing?

The "locking" mechanism of the knee, which occurs when the knee is fully extended during standing, is primarily attributed to the menisci and the unique shape of the femoral condyles. When the knee is extended, the shape of the femoral condyles interlocks with the surface of the tibia, creating a stable position that reduces the need for muscular effort to maintain standing.

Additionally, the menisci — the crescent-shaped cartilage structures located between the femur and tibia — help deepen the surface area for articulation and contribute to the overall stability of the joint by adapting the surfaces of the bones to one another. This anatomical design allows for a secure and stable position, minimizing the risk of injury and providing weight-bearing support.

Other structures, such as ligaments, tendons, and the patella, play vital roles in knee stability and movement; however, they are not the primary contributors to the locking mechanism during standing. The ligaments primarily serve to provide support and prevent excessive movement, while the quadriceps tendon and patella are crucial for extending the knee but do not influence the locking mechanism directly on their own.