PURPOSE: The purpose of this study is to assess the change of the articular cartilage thickness resulting from physiological aging in normal Korean people without any disease in knee joint. MATERIALS AND METHODS: Voluntary participants of 81 cases, physically normal and free from knee joint disease at present or in the past, were chosen for our research program. The subjects were divided into young, middle and old age group respectively for the male and female; and articular cartilage thickness using MRI were measured. RESULT: Each of the three groups reveals the tendency of decrease in the thickness of the knee joint cartilage in all of the age groups along with the increase of the age. The cartilage thickness according to age for both sex, except for the tibial medial condyle, decreased significantly. For the male subjects, the degree of decrease in cartilage thicknes indicates difference in each sections. However, in case of female, the change of articular cartilage thickness in overall sections showed more significantly decreased in young to middle age group than in middle to old age group. CONCLUSION: The results revealed the normal articular cartilage thickness of knee and time that the thickness of articular cartilage was decreased with age. And we could evaluate the severity of degenerative change of articular cartilage by comparison to normal articular cartilage thickness.