Distribution of subchondral bone density and cartilage thickness in the human patella

Subchondral bone density (by means of CT osteoabsorptiometry), and
cartilage thickness (directly measured on photocopies of frozen
sections), were examined in 30 human patellae, with an age range
from 47 to 90 y. A surface demonstration of the distribution was
prepared, and representative pictures produced by summation with a
computer. Subchondral bone-density maxima were found in the
proximal part of the lateral facet, and the density pattern
interpreted as the expression of the long-term distribution of
stress in the joint. It is reasonable to assume that cartilage
thickness, of which two-thirds of the maximum values occupy a
lateral position, is also dependent on the local stress. The 2
distributions show correlation coefficients > 0.5 in
approximately a third of the cases we examined. Displacement of the
higher values of cartilage thickness relative to the subchondral
density maxima is attributed to incongruence in the medial part of
the joint.