Decreased incidence of knee posterior cruciate ligament injury in Australian Football League after ruck rule change.

Objective: To assess whether a rule change introduced in the Australian Football League (AFL) before the start of the 2005 season, to limit the run-up of ruckmen at the centre bounce, has been successful in reducing the incidence of knee posterior cruciate ligament (PCL) injuries.

Design: Cohort study with historical control.

Setting: The AFL competition from 1992 to 2008 inclusive.

Assessment Of Risk Factors: The presence of a rule change (four seasons) compared with the previous 13 seasons (divided into two eras of seven and six seasons).

Main Outcome Measure: Occurrence of knee PCL injury during a regular season or finals match, both from all causes and specifically from centre bounce ruck collision mechanisms.

Results: From 1992 to 1998 there were 11.0 PCL injuries per 10,000 player-hours, with 0.8 ruck injuries per 10,000 centre bounces. From 1999 to 2004, the rates increased to 12.9 per 10,000 player-hours and 5.6 ruck injuries per 10,000 centre bounces (p<0.01). The rates reduced to 5.9 PCL injuries per 10,000 player-hours and 0.9 ruck injuries per 10,000 centre bounces in the period 2005-2008 following the rule change (p<0.01). There was a lower relative risk in 2005-2008 than in 1999-2004 of incurring a centre bounce ruck PCL injury (0.16 (95% CI 0.04 to 0.69)) or of sustaining any PCL injury (0.45 (95% CI 0.28 to 0.75)).

Conclusion: A rule change in the AFL to limit the run-up of ruckmen at the centre bounce has successfully reduced the rate of PCL injuries with this mechanism, with the total incidence of PCL injuries also falling.