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 a verage 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 potent ial radiographic technique for operatively locating the femoral attachment site to within 3 mm is described. During knee flexion in neutral rotation t he 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.m of applied external rotation force, beyond 30 degrees of flexion th e attachment sites rapidly approximated. With the same internal rotation fo rce, beyond 15 degrees of flexion the attachment sites separated. From 60 d egrees to 105 degrees they were greater than 100% of the value in full exte nsion, suggesting significant distraction between the attachment sites. The se changes correlated well with the ligament's change from an 11 degrees po sterior slope in extension to a 19 degrees anterior slope in flexion with n o applied rotation.