The shapes and relative movements of the femur and tibia at the knee.

Unlike the situation at the hip, controversy continues as to the shape of the bones in the knee (for example, are the femoral condyles helical in sagittal section?) and as to the way in which the femur moves on the tibia (for example, does the femur roll-back during flexion?). Although the replaced knee is unlikely to achieve normal kinematics, it seems desirable to understand how far it departs from normal. A knowledge of the normal is also important in the management of ligament injuries. Thus it is desirable to resolve these controversies. We have studied the shape of the bones and the way in which they move in the normal cadaveric knee using MRI as a first step to developing an MRI protocol for establishing the kinematic behaviour of the knee in the clinical setting. Our results have been confirmed in normal volunteers using Open Access and Interventional MRI. The latter enables the knee to be imaged whilst the subject is weight-bearing.