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PURPOSE: To determine the incidence of second anterior cruciate ligament (ACL) injuries in football players after index ACL reconstruction (ACLR). Secondary objectives were to assess second ACL injury rates across subgroups (laterality, sex, age, playing level, graft type, return to play RTP and follow-up duration) and to review factors associated with reinjury. METHODS: A systematic review and meta-analysis were conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, EMBASE and the Cochrane Library were searched from inception to 10 December 2025. Studies reporting second ACL injuries or subsequent ACLRs in football players were included. Incidence was defined as the proportion of players sustaining a subsequent ACL injury or ACLR relative to those undergoing index ACLR. RTP was defined as participation in at least one official match. Key limitations include substantial heterogeneity across studies, the inclusion of mixed data sources and the operational definition of second ACL injury, combining ACL injuries (graft rupture or contralateral tear) or, when not reported, subsequent ACLRs. RESULTS: Thirty-four studies (16,905 players; 50.5% male) were included. The pooled incidence of second ACL injury was 21.6% (95% confidence interval CI 17.9%-25.9%). Contralateral (10.6%, 95% CI 8.0%-13.9%) and ipsilateral injuries (10.4%, 95% CI 8.4%-12.9%) were of similar magnitude. Higher pooled incidence was observed in female (23.5%, 95% CI 18.0%-30.1%) compared with male players (14.5%, 95% CI 14.5%-23.4%), with 30% increased odds (odds ratio OR 1.3, 95% CI 1.1%-1.7%, p < 0.01). Among professionals, incidence was 19.2% (95% CI 15.1%-24.2%). No significant differences were found between hamstring tendon and bone-patellar tendon-bone (BPTB) autografts. The highest rates were observed in players <21 years (31.9%, 95% CI 23.6%-41.6%) and in cohorts with high RTP rates (29.2%, 95% CI 24.7%-34.1%). CONCLUSION: Second ACL injuries are common in football, affecting roughly between one in three to one in five players after ACLR. Higher rates of second ACL injury were observed in female players, younger individuals, those who returned to play, and in studies with longer follow-up duration. Contralateral ACL injuries had a similar magnitude to ipsilateral injuries. No significant differences in ipsilateral ACL reinjury rates were found between hamstrings tendon and BPTB autografts. LEVEL OF EVIDENCE: Level IV, systematic review and meta-analysis.
Personat et al. (2026) studied this question.