Summary

Early ACL reconstruction could play a protective role on the MCL in combined ACL/MCL lesions.

Abstract

Background

Anterior cruciate ligament (ACL) tear impairs knee biomechanics in daily activities and potentially breaks the synergy among the other knee ligaments. Previous studies have demonstrated that the biomechanics of collateral ligaments is influenced by ACL deficiency.

Purpose

To investigate the changes in the elongation patterns of the collateral ligaments and the posterior cruciate ligament (PCL) during the execution of a single-leg squat before and after ACL reconstruction.

Methods

A total of 16 patients (age, 24.9 ± 8.5 years) with ACL deficiency were enrolled in the study. Magnetic resonance imaging scans of the affected knees were used to produce 3-dimensional models of the tibia and femur and to identify insertion sites of the medial collateral ligament (MCL), lateral collateral ligament (LCL), and PCL. Motion capture of a single-leg squat was performed through a biplanar radiographic system. Data were acquired before ACL reconstruction and at a minimum of 18 months (mean, 22.9 ± 4.1 months) postoperatively. The centroids of the ligaments’ insertions were used to calculate the length of the investigated structures during the squat task. Absolute length (L), absolute length increase from an orthostatic resting position (ΔL), and relative length increase (ΔL%) were computed for each ligament, and preoperative and follow-up data were compared using the paired Student t test. The intraclass correlation coefficient was used to compute the reliability of the ligament insertion identification and kinematics between the 2 independent observers.

Results

Significant differences were found in the MCL for absolute length (P = 0.047, d = 0.60) and relative length increase from rest (p = 0.043, d = 0.61) between preoperative and follow-up (ΔLpre = 1.0 mm, ΔLpost = –1.1 mm; difference = 2.1 mm, 2.9%) at 0° to 30° of knee flexion during the descending phase of the single-leg squat. No differences were seen in the elongation patterns of the LCL or PCL from before to after ACL reconstruction.

Conclusion

The MCL was significantly lengthened between 0° and 30° in ACL-deficient knees compared with ACL-reconstructed knees during the descending phase of a single-leg squat. No differences were identified for the LCL or the PCL.