Analysis of passive tibio-femoral joint movement of Beagle dogs during flexion in cadaveric hind limbs without muscle

The aim of this study was to evaluate the normal range of motion of the canine tibiofemoral joint and the movement of the tibia relative to the femur, especially the internal/external rotation under flexion. Right stifle joints were harvested from eight skeletally mature Beagle dogs, which were euthanized for reasons unrelated to this study. All muscle tissue was removed from the limbs prior to testing. Flexion and extension tests were conducted using a robotic manipulator with six degrees-of-freedom. Cranial/caudal and medial/lateral displacement and varus/valgus and internal/external rotation were measured at various degrees of flexion. We observed that the tibia rotated internally at an increasing flexion angle with mean peak internal and external rotations of 20.0 ± 13.8° and 4.5 ± 3.6°, respectively. The tibia also tended to displace cranially at an increasing flexion angle, with a mean peak cranial displacement of 8.9 ± 4.4 mm; there was minimal medial displacement when increasing the flexion angle. Valgus rotation also tended to occur at an increasing flexion angle. During the flexion of the canine stifle joint, approximately 20° of internal tibial rotation occurred around the longitudinal axis, along with a rollback motion involving the cranial displacement of the tibia.