Knee function, pain and magnetic resonance imaging abnormalities in Australian Rules Football players: a cohort study

Abstract

Background/Introduction: Australian Rules Football (ARF) has a strong following in Australia and has one of the highest injury rates amongst collision sports worldwide.1 Knee injuries are common in ARF and are associated with both short- and long-term functional disability.1,2 Magnetic resonance imaging (MRI) has revolutionised our understanding of knee pathology, with early detection of knee abnormalities that eventually lead to significant disability.3 This is the first study to determine the prevalence of MRI assessed knee abnormalities in ARF players and describe their associations with function, pain, past and incident injury and surgery history. Methods: 58 of 75 male players (aged 16-30 years) from the Tasmanian State Football League underwent MRI of both knees early in the season, assessing cartilage defects, bone marrow lesions (BMLs), meniscal tears/ extrusion and effusion. History of knee injury and surgery, and knee pain and function (VAS and KOOS) and incident knee injuries were assessed. Measures were repeated at the end of the season (3-5 months later). Results: MRI knee abnormalities were common at baseline (67% BMLs, 16% meniscal tear/extrusion, 43% cartilage defects, 67% effusion-synovitis). At baseline, presence of BMLs was associated with higher knee pain and dysfunction (VAS 3 vs 17, P < 0.01; KOOS 6 vs 18, P = 0.03) in the right but not left knee, and higher prevalence of previous knee injury and surgery (21% vs 53%, P = 0.01; 0% vs 18%, P = 0.03 respectively). Findings were similar for meniscal tears/extrusion. Previous injury and previous surgery were more common in those with an effusion and with cartilage defects respectively. Incident knee injuries were associated with worsening knee pain and function (VAS -6 vs 27, P < 0.01; KOOS -5 vs 21, P < 0.01), presence of new or enlarging BMLs (22% vs 67%, P < 0.01) and incident cartilage defects (3% vs 17%, P = 0.03). Interestingly, knee abnormalities were also common in asymptomatic players with no prior history of injury or surgery (5-59%). Conclusions: As far as we are aware, this is the first study to examine the clinical significance of MRI abnormalities in AFL players. Structural abnormalities commonly seen in osteoarthritis are also common in subelite ARF players. Their associations with injury and surgery suggest they could be clinically important; however, the implication for long-term knee health is unknown especially in asymptomatic players.