Objective To examine the in vivo accuracy and precision of magnetic resonance imaging (MRI)–based assessment of cartilage loss in patients with severe osteoarthritis (OA) of the knee. Methods High‐resolution MRI images of the tibial cartilage were obtained in 8 patients prior to total knee arthroplasty, using a water‐excitation gradient‐echo MRI sequence (acquisition time 6 minutes 19 seconds; spatial resolution 1.2 × 0.31 × 0.31 mm3). The MRI measurements were repeated after joint repositioning. The precision of the cartilage volume and thickness computations was determined after 3dimensional reconstruction. During surgery, the tibial plateaus were resected, and the MRI data were compared with water displacement of surgically retrieved cartilage. Results The standard deviation (coefficient of variation) of repeated tibial cartilage volume measurements was 56 mm3 (5.5%) medially and 59 mm3 (3.8%) laterally. The deviation from surgically removed tissue was −13%, on average, with a high linear correlation between both methods (r = 0.98). In patients with varus OA, the tissue loss was estimated to be 1,290 mm3 in the medial tibia and 1,150 mm3 in the lateral tibia, compared with the data in healthy volunteers. Conclusion Noninvasive quantitative MRI‐based analysis of cartilage morphometry in severe OA is accurate, precise, and displays high potential diagnostic value.

Objective Alterations of cartilage morphology and mechanical properties occur in osteoarthritis, but it is unclear whether similar changes also take place physiologically during aging, in the absence of disease. In this in vivo study, we tested the hypothesis that thinning of knee joint cartilage occurs with aging and that elderly subjects display a different amount of cartilage deformation than do young subjects. Methods We evaluated 30 asymptomatic subjects ages 50–78 years. Morphologic parameters for the knee cartilage (mean and maximum thickness, surface area) were computed from magnetic resonance imaging data. Results were compared with those in 95 young asymptomatic subjects ages 20–30 years. Deformation of the patellar cartilage was determined after the subjects performed 30 knee bends. Results There was a significant reduction of patellar cartilage thickness in elderly women (−12%; P < 0.05), but not in elderly men (−6%). Femoral cartilage was significantly thinner in both sexes (−21% in women, −13% in men; P < 0.01), whereas tibial cartilage thickness displayed only nonsignificant trends (−10% in women, −7% in men). Patellar cartilage deformation was −2.6% in elderly women and −2.2% in elderly men. These values were significantly lower (P < 0.05) than those in young subjects. Conclusion We confirmed the hypothesis that knee cartilage becomes thinner during aging, in the absence of cartilage disease, but that the amount of reduction differs between sexes and between compartments of the knee joint. We show that under in vivo loading conditions, elderly subjects display a lower level of cartilage deformation than do healthy young subjects.

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