Anatomy and kinematics of the lateral collateral ligament of the knee.

The anatomy and kinematics of the lateral collateral ligament were studied in 10 unembalmed limbs and 20 isolated femurs and fibulas. The ligament's average overall length was 66 mm (range, 59 to 74) and the average greatest dimension of its thin middle portion was the anteroposterior dimension of 3.4 mm (range, 3 to 4). The center of the femoral attachment site was 3.7 mm posterior to the ridge of the lateral epicondyle, not at it apex. A potential radiographic technique for operatively locating the femoral attachment site to within 3 mm is described. During knee flexion in neutral rotation the distance between the femoral and fibular attachment sites of the lateral collateral ligament decreased to 88% of its value in full extension. With 6.5 N x m of applied external rotation force, beyond 30 degrees of flexion the attachment sites rapidly approximated. With the same internal rotation force, beyond 15 degrees of flexion the attachment sites separated. From 60 degrees to 105 degrees they were greater than 100% of the value in full extension, suggesting significant distraction between the attachment sites. These changes correlated well with the ligament's change from an 11 degrees posterior slope in extension to a 19 degrees anterior slope in flexion with no applied rotation.