The popliteofibular ligament. Rediscovery of a key element in posterolateral stability.

We have recently become aware of a strong direct attachment of the popliteal tendon to the fibula. To investigate the importance of this attachment, we examined 20 cadaveric knees. The popliteofibular ligament was identified in all 20 knees. The cross-sectional area of the popliteofibular ligament was 6.9 +/- 2.1 mm2, compared with 7.2 +/- 2.7 mm2 for the lateral collateral ligament. Biomechanical testing of these structures, simulating a purely varus stress on the knee, revealed that the lateral collateral ligament always failed first, followed by the popliteofibular ligament, and then the muscle belly of the popliteus. The mean maximal force to failure of the popliteofibular ligament approached 425 N (range, 204 to 778), compared with 750 N (range, 317 to 1203) for the lateral collateral ligament. Our results indicate that the popliteofibular ligament contributes to posterolateral stability.