Increased Hazard Ratio of a Second ACL Injury After Return to Sport for Each Positive Hypermobility Test on the Beighton Score: A Registry Study: A Registry Study

Background: Generalized joint hypermobility (GJH) has been associated with increased risk of second anterior cruciate ligament (ACL) injury. The clinical diagnosis of GJH relies on a binary threshold of positive joint hypermobility tests, based on age and patient sex, which may overlook the degree of hypermobility. Objectives: To analyze the association between the number of positive joint hypermobility tests on the Beighton Score and the hazard of second anterior cruciate ligament (ACL) injury in patients who return to sport (RTS) after primary ACL reconstruction, which included secondary, stratified analyses of graft rupture and contralateral ACL injury. Design: Registry study. Methods: Data were extracted in January 2026 from an ACL-rehabilitation-specific registry, Project ACL. Included patients were 15–50 years who underwent primary ACL reconstruction with hamstring tendon or bone–patellar tendon–bone autograft, had a documented Beighton Score, participated in knee-strenuous sports before injury, had RTS, reported second ACL injury or had ≥ 1 year follow-up without second ACL injury after RTS. Multivariable Cox proportional hazard regression was used to estimate the cause-specific hazard ratio (HR) of second ACL injury (measured from RTS) based on the Beighton Score, adjusted for age, return to pre-injury physical activity level or higher, graft choice, knee hyperextension (≥ 10° knee extension), and patient sex, accounting for competing risks. Results: The analysis included 935 patients (mean age 23.7 ± 7.8 years, 51.4% female), with median Beighton Score of 2 (interquartile range: 4). The median follow-up time was 54.4 months. The cumulative incidence of second ACL injury after RTS was 13.1%. Specifically, the cumulative incidence for graft rupture was 7.4% and 5.7% for contralateral ACL injury. For the primary outcome, each additional positive joint hypermobility test on the Beighton Score was associated with a significantly increased hazard of second ACL injury (adjusted HR: 1.10 (95% CI 1.003–1.22, p = 0.044). For the secondary outcomes, each additional test was associated with an increased hazard of graft rupture (adjusted HR: 1.15, 95% CI 1.01–1.30, p = 0.031), whereas no statistically significant association was observed for contralateral ACL injury. Conclusions: The HR of second ACL injury (graft rupture or contralateral ACL injury) after RTS in patients who had undergone primary ACL reconstruction increased by 10%, and by 15% for isolated graft rupture, for each positive joint hypermobility test on the Beighton Score, while no association was observed for contralateral ACL injury.