The Changes of Anterior Displacement in Combined ACL / MCL Injured Knee after MCL Healing

Kim, Hyoung Soo; Park, Seung Rim; Kang, Joon Soon; Lee, Woo Hyeong; Yeoum, Seung Hoon

Abstract

The medial collateral ligament(MCL) of the knee is the well established secondary restraint to the anterior displacement of the knee joint. However, there has been no report about the estimation of the anterior displacement in combined ACL(anterior collateral ligament) and MCL injures according to period when they were treated with conservative measures. This prospective study evaluated the changes of anterior displacement over time in combined ACL/MCL injury as the MCL injury heals after initial conservative measures. 19 patients who had combined ACL/MCL injury were followed during twelve months after injury. All patient had a positive Lachman test and were evaluated the side to side differences on KT-2000 knee arthrometer(Medmetric, San Diego, California) testing under 20 Ibs anterior tibial loading at 30 degree knee flexion. The stability of the knee was assessed using KT-2000 knee arthrometer every 8 weeks with clinical examination prospectively. They were treated with CI (Combined instability) brace (Smith & Nephew, Carlsbad, California) as conservative measures. Overall, Initial side to side difference of the anterior displacement was averaged 5.21mm (range,4.0-7.0mm) and 3.30mm (range,2.0-5.5mm) finally. According to the classification of MCL injury, in Grade III groups, they had the greatest initial anterior displacement about 6.4mm, but tight- ened the most to 3.08mm finally. In Grade II and Grade I groups they showed 2.97mm and 2.13mm side to side difference (p>0.01). However in Grade I, the anterior displacement were decreased by 4 months after injury but, it were increased at 6 months after injury. In Grade II and III, the decrement of the anterior displacement were continued by 6 months after injury, but they were not changed after that. The data was analyzed by General Linear Model Procedure method. Conclusively, the anterior displacement of knee in patients with combined ACL/MCL injury was diminished with the time in the majority of patients as the MCL healed. It means that the MCL was the stabilizer to the anterior displacement of the knee under the anterior tibial loading.