What is the closed-pack position of the tibiofemoral joint?

What is the closed-pack position of the tibiofemoral joint?

• A. Full extension with tibial ER
• B. Full extension with tibial IR
• C. 90 degrees flexion with tibial ER
• D. Full flexion

Answer: (A)

Closed-pack means the joint surfaces are maximally congruent and the ligaments are taut, giving the joint its most stable, locked position. For the tibiofemoral joint, this occurs in full knee extension with the tibia rotated externally relative to the femur. In this configuration the cruciate and collateral ligaments are taut and the articular surfaces line up snugly, producing maximum stability and minimal accessory motion. The external rotation of the tibia during full extension (the end of the screw-home mechanism) is what achieves that optimal alignment. Positions with rotation absent, or with the knee at 90 degrees of flexion or full flexion, do not produce this same level of congruence and ligament tension, so they are not the closed-pack position.

Closed-pack means the joint surfaces are maximally congruent and the ligaments are taut, giving the joint its most stable, locked position. For the tibiofemoral joint, this occurs in full knee extension with the tibia rotated externally relative to the femur. In this configuration the cruciate and collateral ligaments are taut and the articular surfaces line up snugly, producing maximum stability and minimal accessory motion. The external rotation of the tibia during full extension (the end of the screw-home mechanism) is what achieves that optimal alignment. Positions with rotation absent, or with the knee at 90 degrees of flexion or full flexion, do not produce this same level of congruence and ligament tension, so they are not the closed-pack position.