Structural abnormalities commonly seen in osteoarthritis are also common in AFL players and are associated with pain and loss of function, according to Professor Tania Winzenberg from the Menzies Institute for Medical Research in Hobart.

“We need to define which lesions are pathological, the implications for long-term knee health, and what can be done to reduce the burden,” she said.

Professor Winzenberg and her colleagues recruited 58 of 75 players from the Tasmanian State Football League and performed MRI scans of both knees.

They averaged 21 years of age (ranging from 16 to 30) and had played Australian Rules football for between 1 and 21 years. About half (52%) had a history of a previous knee injury.

Baseline MRIs early in the season revealed a high rate of abnormalities, including 67% with bone marrow lesions (BMLs), 16% with meniscal tears or extrusions, 43% with cartilage defects and 67% with an effusion.

“At baseline, the presence of BMLs and meniscal injuries was associated with higher knee pain and dysfunction, and a higher prevalence of previous knee injury and surgery,” she said.

“However, 54% of those with BMLs did not report any symptoms or history of trauma or surgery.”

Previous injury was more common in those with an effusion, and previous surgery was more common in those with cartilage defects.

Forty four players had repeat MRIs at the end of the season. Ten reported a knee injury, and they had worsening knee pain and function, new or enlarging BMLs and new cartilage defects.

“We don’t yet know if the new BMLs are an acute response to injury or a normal stress response to heavy loading,” Professor Winzenberg said.

Knee injuries are famously common in elite AFL players, with anterior cruciate ligament injuries generally being the most serious.