The impact of isolated ACL and MCL injuries on career longevity and performance metrics in elite rugby union players.

BACKGROUND

Knee ligament injuries are common in elite rugby union players and are associated with performance limitations. However, comparative data on long-term performance and career patterns after isolated anterior cruciate ligament (ACL) versus medial collateral ligament (MCL) injuries remain limited.

METHODS

A retrospective review of elite rugby union players who sustained an isolated partial or complete ACL or MCL tear from 2013 to 2025 was performed. Data were collected from rugby databases and media reports, and included player demographics, injury characteristics, and performance metrics. A Wilcoxon signed rank test was used to compare pre-injury and post-injury performance metrics, with a p value < 0.05 determined as statistically significant.

RESULTS

Twenty-eight players sustained ACL injuries and 23 sustained MCL injuries. At 9.8 ± 3.1 months, 96.4% of ACL-injured players returned to sport, while 100% of MCL-injured players returned at 1.9 ± 2.1 months. ACL-injured players demonstrated significant declines in games played, tries, and points scored in the season following injury. Over time, performance largely stabilized, but total seasons played decreased. Players with MCL injuries demonstrated short-term performance declines but played a. similar number of seasons before and after injury. Re-injury occurred in 17.9% of ACL cases and 13.0% of MCL cases, with greater re-injury frequency and shorter intervals between injuries in the ACL cohort.

CONCLUSION

ACL injuries in elite rugby union players were associated with longer return to sport (RTS) times and fewer post-injury seasons despite recovery of performance metrics. MCL injuries allowed faster RTS and preserved career length but were associated with decreased performance. Re-injury led to further performance decline in both cohorts. These findings highlight distinct patterns of career and performance impact following ACL versus MCL injury in elite rugby union players.

LEVEL OF EVIDENCE: IV.