Mechanical overload of a single compartment induces early degenerative changes in the rabbit knee: a preliminary study.

The purpose of this experiment was to determine whether mechanical overload of a single compartment of the knee in rabbits via proximal tibial osteotomy could produce early changes consistent with degenerative arthritis. Ten New Zealand white female rabbits were allocated into two groups. Group 1 (five animals) underwent a right 20 degrees valgus proximal tibial osteotomy to overload the lateral compartment of the knee. Group 2 (five animals) underwent a tibial osteotomy without malalignment (sham controls). The osteotomies were stabilized with a mini AO/ASIF plate and screws, allowing early mobilization. The left leg in each animal was left intact and served as a control. Animals were sacrificed after 3 months. Histological grading of the cartilage was performed according to Mankin et al. The mean histological gradings for the right minus the left knee were the same for the lateral and medial compartments in the 0 degrees sham osteotomy group. However, the mean histological grading of the "overloaded" lateral compartment was 2.4 times greater than the medial compartment in the 20 degrees valgus osteotomy group. These findings suggest that histological evidence of degenerative changes can be surgically induced in the rabbit knee by creating a biomechanical overload of one compartment.