Background: The objective of the study is to describe temporal trends and regional variations in the use of knee magnetic resonance imaging (MRI), knee arthroscopy and total knee replacement surgery in Australians older than 55 years. Methods: Design: A retrospective descriptive study using routinely collected administrative data. Main outcome measures: Age-standardized rates of knee MRI, knee arthroscopy and knee replacement surgery from 2003 to 2017. Results: Knee MRI rates increased from 216/100 000 in 2003, to 1509/100 000 in 2017 (sevenfold relative increase). Knee arthroscopy rates initially increased from 372/100 000 in 2003 to a maximum of 475/100 000 in 2011, before declining to 283/100 000 in 2017. Knee joint replacement surgery increased from 535/100 000 in 2003 to 840/100 000 in 2017 (57% relative increase). The use of MRI increased in all regions of Australia but to differing extents. Knee arthroscopy rates declined in all regions from 2011, but to differing extents. Knee joint replacement surgery increased at roughly the same rate across Australia. Conclusion: Knee arthroscopy rates increased before declining modestly in more recent years, most likely in response to evidence against its effectiveness. Knee MRI rates have continued to increase despite consistent recommendations against their routine use in the evaluation of knee pain. Future research could investigate potential drivers of the increased use of MRI, and of the continued use of arthroscopy. Further exploration of the extent to which either procedure explains the increase in numbers of knee joint replacements is also warranted.