The effect of internal and external laxity on unconstrained multi-axial knee joint motion in sheep during late swing phase of walking
The purpose of this thesis was to observe and compare the unconstrained motion of ovine stifles under physiologic loading conditions at 20 degrees of flexion upon internal and external moment loading. Nine ovine stifles were used to model the human knee: 5 healthy controls and 4 stifles with osteoarthritis degeneration subsequent to two common human knee injuries (partial medial meniscectomy and complete ACL transections). Each knee was cycled in 1 Nm increments from 3 Nm of internal moment load through to 3 Nm of external moment load using a 6 DOF parallel robot; the unconstrained multi-axial joint motion was recorded. In healthy specimens, the tibia travelled an average of 3.7 mm posteriorly, 1.5 mm distally, 1.5 mm medially, 9.0 deg varusly and 22.9 deg externally. The joint motion in the surgically destabilized stifles was more variable; this was due, in part, to a more lax joint and the presence of osteophytes on the femoral condyles, intercondylar notch and the tibial plateau.