Analysis of tibiofemoral cartilage deformation in the posterior cruciate ligament-deficient knee.

BACKGROUND: Degeneration of the tibiofemoral articular cartilage often develops in patients with posterior cruciate ligament deficiency, yet little research has focused on the etiology of this specific type of cartilage degeneration. In this study, we hypothesized that posterior cruciate ligament deficiency changes the location and magnitude of cartilage deformation in the tibiofemoral joint.

METHODS: Fourteen patients with a posterior cruciate ligament injury in one knee and the contralateral side intact participated in the study. First, both knees were imaged with use of a specific magnetic resonance imaging sequence to create three-dimensional knee models of the surfaces of the bone and cartilage. Next, each patient performed a single leg lunge as images were recorded with a dual fluoroscopic system at 0 degrees, 30 degrees, 60 degrees, 75 degrees, 90 degrees, 105 degrees, and 120 degrees of knee flexion. Finally, the three-dimensional knee models and fluoroscopic images were used to reproduce the in vivo knee position at each flexion angle with use of a previously described image-matching method. With use of these series of knee models, the location and magnitude of peak tibiofemoral cartilage deformation at each flexion angle were compared between the intact contralateral and posterior cruciate ligament-deficient knees.

RESULTS: In the medial compartment of the posterior cruciate ligament-deficient knees, the location and magnitude of peak cartilage deformation were significantly changed, compared with those in the intact contralateral knees, between 75 degrees and 120 degrees of flexion, with a more anterior and medial location of peak cartilage deformation on the tibial plateau as well as increased deformation of the cartilage. In the lateral compartment, no significant differences in the location or magnitude of peak cartilage deformation were found between the intact and posterior cruciate ligament-deficient knees.

CONCLUSIONS: The altered kinematics associated with posterior cruciate ligament deficiency resulted in a shift of the tibiofemoral contact location and an increase in cartilage deformation in the medial compartment beyond 75 degrees of knee flexion. The magnitude of the medial contact shift in the posterior cruciate ligament-deficient knee was on the same order as that of the anterior contact shift.