Mechanical properties of the posterolateral structures of the knee.

Background: The individual biomechanical strength properties of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon have not been well elucidated by previous studies. To define the necessary strength requirements for a posterolateral knee reconstruction, these properties for the main individual structures of the posterolateral knee need to be defined.

Hypothesis: The biomechanical failure properties of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon can be determined by cadaveric testing.

Study Design: Descriptive laboratory study.

Methods: Each structure was individually isolated in 8 fresh-frozen, nonpaired cadaveric knees and loaded to failure at more than 100%/s.

Results: The mean ultimate tensile strength of the fibular collateral ligament was 295 N, the popliteofibular ligament was 298 N, and the popliteus tendon was 700 N. The mean cross-sectional areas of these same structures at their midpoints were 11.9 mm2, 17.1 mm2, and 21.9 mm2, respectively. Although the stiffness of the fibular collateral ligament (33.5 N/m) was similar to that of the popliteofibular ligament (28.6 N/m), the popliteus tendon was significantly stiffer than both (83.7 N/m).

Conclusion: The popliteofibular ligament, fibular collateral ligament, and popliteus tendon can resist fairly large loads before failure. Knowledge of the strengths of the main native posterolateral knee stabilizers will assist with reconstructive graft choices for these structures.