The effects of angular deformities of the tibia on the contact areas and
pressures on cartilage in the knee were measured with use of
pressure-sensitive film. Six cadaver knees were mounted in a test-frame,
such that the offset and tilt of the knee relative to the load-axis
simulated that due to angular deformities of the tibia of 5, 10, 15, or 20
degrees of varus or valgus at the levels of the proximal, middle, and
distal thirds. Angulation had little effect on the contact area. The change
in pressure was least for fractures of the distal third and greatest for
fractures of the proximal third. For example, a 20-degree angulation of the
distal third increased the maximum contact pressure by an average of 26 per
cent in the compartment toward the load-axis and reduced it by 32 per cent
in the opposite compartment. With an angulation of 20 degrees at the level
of the proximal third of the tibia, the increase in pressure averaged 106
per cent and the decrease averaged 89 per cent. The changes in pressure
with fractures at the middle third were between these extremes.