Rupture of the anterior cruciate ligament (ACL) in the knee is the injury that causes the longest lasting disability to footballers. Now a new study from Denmark has shed unexpected light on the causes of this injury that should help to prevent it in future.

The researchers, from a hospital sports clinic, surveyed 113 patients, consecutively admitted to their clinic with an ACL rupture sustained while playing football, to analyse the mechanism behind their injury.
Their key findings – some of them surprising – were as follows:

• Goalies sustained as many ACL injuries as other players;
• 62 ACL injuries occurred on the opponent’s half of the field – 18 of them inside the penalty box;
• There was no statistical difference between the numbers of players in defensive and offensive roles at the time of injury;
• 30 of the injured players were in contact neither with other players nor the ball at the time of injury and 58 were in contact with the ball alone;
• Only 17 sustained an ACL rupture while being touched or pushed;
• 56 had intended to change their direction towards the side of the injured knee at the time the ACL was torn, while only ten had intended to turn towards the uninjured side;
• 26 sustained their injury when landing after heading the ball, of whom 20 were being tackled by an opponent in the air, so jeopardising their landing;
• 19 had a previous injury other than an ACL injury in the now ACL-injured knee, compared with five in the other knee.

The researchers draw two main conclusions from their findings:

First, that ‘the mechanism behind ACL rupture differs from that of other soccer-related injuries because only a small fraction of the injured players had contact with another player at the time of the accident. We therefore conclude that tackling and kicking do not contribute significantly to ACL ruptures in soccer’.

Secondly, two distinctive actions – change of direction and landing after heading – are responsible for the vast majority of ruptures. If players could be trained to perform these particular moves more safely, the risk of injury could be substantially reduced.

Int J Sports Med 2006; 27:75-79