THE DISTRIBUTION OF CARTILAGE THICKNESS WITHIN THE JOINTS OF THE LOWER-LIMB OF ELDERLY INDIVIDUALS

The objective of this study was to investigate the normal distribution of cartilage thickness in the major joints of the lower limb in elder ly individuals. A 12.5 MHz ultrasound transducer was used to measure t he cartilage thickness in the right and left hip, knee and ankle joint of 10 individuals aged between 62 and 99 y. Distribution patterns of cartilage thickness were derived by b-spline interpolation and the ave rage distribution computed in each surface. The maximum cartilage thic kness in the hip joint was 2.6 (+/-0.36) mm and the mean thickness 1.3 (+/-0.17) mm. The CV% (a measure of thickness inhomogeneity within th e joint surface) was 32 %. In the knee, the maximal and mean values we re 3.8 (+/-0.46) mm and 1.9 mm (+/-0.24) mm, respectively (CV % =34 %) , and in the ankle 1.7 (+/-0.25) mm and 1.0 (+/-0.16) mm (CV % =32 %). Systematic differences existed between both sides in the knee, the di stal femur showing a significantly greater thickness on the right. Whi le the mean and maximal thicknesses were systematically higher in the knee than in the hip, and in the hip higher than in the ankle (P < 0.0 5), there were no systematic differences in the thickness inhomogeneit y of; the 3 joints. Only the malleolus showed a somewhat more uniform thickness than the other joint surfaces. The variablity between indivi duals was similar for all joints for mean thickness, but the interindi vidual variability of the maximal thickness values was highest in the knee and lowest in the ankle. Whereas the cartilage thickness distribu tions in the joints of the lower limb have been suggested to reflect t he pressure distribution within the articular surface, the absolute th ickness is proposed to be a function of dynamic loading (range of moti on) during gait, rather than being a reflection of the static articula r pressure.