To improve knowledge of the current trends in the number and incidence of age-related minor trauma knee fractures, we selected from the National Hospital Discharge Register all patients 60 years old or older who were admitted to Finnish hospitals in 1970-1972, 1974-1975, 1978-1980, 1983-1985, 1988-1989 and 1991-1994 for primary treatment of first knee fracture. The knee fracture was defined to be a "minor trauma" fracture if it had occurred as a result of a fall from standing height or less. We also predicted fracture development until the year 2020 by a regression model, which took into account the predicted changes in fracture incidences and population at risk. The number and incidence (per 100,000 persons) of minor trauma knee fractures in Finnish women aged 60 years or more clearly increased during the study period, from 219 (number) and 55 (incidence) in 1970 to 579 and 100 in 1994. Women's age-adjusted incidence of these fractures also showed an increase, from 58/100,000 in 1970 to 93/100,000 in 1994. If this trend continues, there will be about 2 times more minor trauma knee fractures in Finnish women in the year 2020 than there were in 1994. In Finnish men aged 60 years or more the absolute numbers and incidences of these fractures did not show consistent trend changes over time. We conclude that the number of minor trauma knee fractures in elderly Finnish women in increasing more rapidly than can be accounted for by the demographic changes alone and therefore effective preventive measures should urgently be adopted to control the increasing burden of these age-related fractures.