EVALUATION OF SERUM RELAXIN CONCENTRATIONS AND KNEE VALGUS AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

BACKGROUND: Athletes who sustain an anterior cruciate ligament (ACL) injury are more likely to develop adverse health outcomes, such as knee osteoarthritis, knee pain, and obesity. It is assumed that the long-term consequences of ACL reconstruction are caused by the reconstruction itself. Studies have observed that relaxin, a peptide hormone similar in structure to insulin, interferes with the structural integrity of the ACL and elicits long term effects on bone, joint, muscle, and tendon health. Given the known effects of relaxin, it is reasonable to wonder if relaxin contributes to the development of these long-term health outcomes, independently of the ACL injury. HYPOTHESIS/PURPOSE: The purpose of this study was to evaluate knee valgus and serum relaxin concentrations (SRC) in athletes who have and have not sustained an ACL injury. It was hypothesized that athletes who previously tore their ACL would have higher SRC and more knee valgus than those who were injury free. METHODS: Twenty-two female athletes participated. Participants were assigned to one of two groups: ACL injury (6.0 ± 3.3 years after surgery, N = 4) and injury free (N = 18). Kinematic data were collected at 100 Hz using The MotionMonitor. Participants performed a single leg squat (SLS), single leg crossover dropdown (SCD), and drop vertical jump (DVJ) at two different time points in their menstrual period: pre-ovulatory phase and mid-luteal phase. Blood samples were collected when SRC are measurable (mid-luteal phase), and SRC were determined using a Quantikine Human Relaxin-2 Immunoassay. RESULTS: Independent samples t-tests revealed significant differences between those who tore their ACL and those who were injury free in SRC and knee valgus during the SLS in the mid luteal phase, DVJ in both phases, and SCD in both phases. Specifically, the participants who tore their ACL had significantly higher SRC and more knee valgus than those who did not tear their ACL. CONCLUSION: These findings suggest that a previous ACL injury could place one at an increased risk of re-tear and other adverse effects on their joints, muscles, and tendons. Thus, further investigating hormonal risk factors during long term monitoring of recovery is needed.