Are physical activity or body mass index associated with subsequent knee injuries in young female athletes?

Abstract

Introduction: Anterior cruciate ligament (ACL) injuries are devastating for young, active individuals, with up to 50% developing osteoarthritis (OA) before aged 40 years. Subsequent knee injury rates are high and lead to even poorer long-term joint health. At 2-3 years after ACL reconstruction (ACLR), the relationships between known modifiable OA risk factors [e.g. moderate and vigorous physical activity (MVPA), body mass index (BMI)] and subsequent knee injury is unknown. The objective of this study was to determine the odds of subsequent (new or recurrent) traumatic knee injury in a cohort of young females with ACLR 2-3 years post-surgery compared with healthy matched-controls. Secondary objectives were to (i) explore the relationships of MVPA and BMI with traumatic knee injury; (ii) document self-reported MVPA satisfaction and beliefs about future OA. Methods: Fifty-one females (aged 14-22 years) with prior (1-2 years) sport-related unilateral ACLR and 51 age-and-sport-matched controls underwent assessment of MVPA (GT3X accelerometers) and BMI. One year later, participants self-reported subsequent (new or recurrent knee injuries), return to sport, MVPA satisfaction, and beliefs about OA risk. Bivariable conditional logistic regression explored the association of knee injury with (i) group (injury/control), (ii) MVPA and (iii) BMI. Beliefs about MVPA satisfaction and OA risk was reported descriptively. Results: At 1 year follow-up (n=101), 19.6% of injured cohort and 6.0% of control participants sustained subsequent knee injuries. The odds of traumatic knee injury for the injury group increased 7-fold over controls [OR=7.00 (95% CI=0.86,56.90)]. Odds ratios (OR) for MVPA and BMI were 0.98 (95%CI= 0.93,1.03) and 1.24 (95%CI=0.85,1.82) respectively. Just over half (55%) of injury participants and 66% of controls were satisfied with their MVPA, while 82% of injury participants believed they had increased knee OA risk compared to someone who had never had a knee injury. Discussion: In the 2-3 years following ACLR, one in five young females had a subsequent traumatic knee injury. Based on the point estimate, injured participants were more likely to suffer a traumatic knee injury than matched controls. BMI was not associated with increased odds of a subsequent traumatic knee injury. Given participation in MVPA did not increase odds of knee injury and the high level of dissatisfaction with MVPA reported in this cohort, in-depth conversations between clinicians and patients who have had ACLR regarding enjoyable and sustainable MVPA participation are encouraged to promote long term joint health. Conflict of interest statement: We acknowledge no conflict of interest of relevance to the submission of this abstract.