KINEMATIC CONSEQUENCES OF CHRONIC ACL INJURY

Abstract

Introduction Late degeneration of the ACL injured knee may be in part due to repeat injury, but also due to aberrant kinematics altering the wear pattern at the chondral surface. The aim of this study was to use tibio-femoral contact mapping by MRI to examine kinematic changes due to chronic ACL deficiency.

Methods Twenty-three subjects with a history of chronic ACL deficiency (mean 18 years since injury) performed a closed chain leg press, relaxed and against a 15 kilogram weight. MRI recorded the tibio-femoral contact position at 15° intervals from 0° to 90° of knee flexion. Intra-articular pathology was assessed for all subjects by MRI, and at arthroscopy for 10 subjects.

Results The tibio-femoral contact pattern of the ACL injured knee differed from the healthy contralateral knee (p=0.003). This difference was greatest in the medial compartment, particularly at 0° and 15° of knee flexion (p< 0.01), with the femur two millimetres (mean, SD 3.2 mm) posterior on the tibial plateau. Damage to the chondral surface was seen in the medial compartment in 16 subjects and lateral compartment in 12; medial meniscus damage was present in 16 subjects and lateral meniscus in 15. Chondral surface damage correlated with the difference in the tibio-femoral contact pattern between the healthy and injured knee in the medial compartment of the knee. Joint damage was not related significantly to time since injury, or Cincinnati knee score. Joint damage was related to level of sports participation, but probably indicates that as the joint failed, subjects curtailed their activity.

Conclusions The kinematic consequences of chronic ACL injury may in part be responsible for the pattern of degenerative change, especially in the medial compartment of the knee.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.