OBJECTIVE: To determine the functional and radiological status of knee joints of retired Australian Rules footballers compared with those of active community members. DESIGN: Retrospective cohort study. PARTICIPANTS: Fifty retired elite footballers aged 34-85 years (mean, 53.7 years; SD, 11.4) from four AFL clubs and 50 age-matched controls (35-79 years; mean, 55.7 years; SD, 12.4) who had played no contact sport since their teenage years. MAIN OUTCOME MEASURES: Severity of knee functional osteoarthritis as determined by a questionnaire, and assessment of osteoarthritis by posteroanterior weight-bearing radiographs taken of both knees of each participant in 45-degree flexion. RESULTS: After adjusting for age, height, weight and body mass index, footballers had a significantly greater prevalence (P < 0.0001) and severity (P < 0.05) of functional and radiological osteoarthritis than controls. Footballers with a history of intraarticular ligamentous and/or meniscal injury (Group 1) had a greater risk of functional osteoarthritis (P = 0.002) and radiological (P = 0.067) osteoarthritis than those with a history of collateral ligament injury or no injury (Group 2). Compared with controls, the odds of developing moderate to severe levels of functional and radiological osteoarthritis were 6.9 times (95% CI, 1.6-29.7; P = 0.01) and 105.0 times (95% CI, 11.8-931.8; P < 0.0001), respectively, those in Group 1 footballers and 3.6 times (95% CI, 0.8-16.2; P = 0.10) and 17.7 times (95% CI, 2.2-146.2; P = 0.0075), respectively, those in Group 2 footballers. CONCLUSIONS: Elite Australian Rules footballers have a significant risk of both functional and radiological osteoarthritis, and a history of intra-articular ligament or meniscal injury increases this risk.