Author(s): TECIOIU, I., STANCU SMARANDA, A.M., CARAMOCI, A., Institution: NATIONAL INSTITUTE OF SPORTS MEDICINE, Country: ROMANIA, Abstract-ID: 1650

INTRODUCTION:
Anterior cruciate ligament (ACL) injuries represent one of the most severe orthopedic pathologies in sports. Women exhibit an incidence rate 2 to 6 times higher than men, depending on the specific sport practiced. Beyond biomechanical and anatomical factors, hormonal variations during the menstrual cycle constitute a critical physiological risk factor, directly influencing ligamentous laxity and neuromuscular control.

METHODS:
A systematic literature review was conducted using PubMed, Scopus, and Cochrane databases, including studies published within the last 10 years. Parameters analyzed included estrogen and progesterone levels, joint laxity measured via arthrometry, and injury incidence during the follicular, ovulatory, and luteal phases.

RESULTS:
* The Critical Phase: Most studies identify the maximum risk of injury during the late follicular (pre-ovulatory) phase. At this stage, estrogen levels peak in the absence of a compensatory level of progesterone.
* Physiological Mechanism: Estrogen reduces collagen synthesis and increases collagenase activity through specific receptors (ER alpha and ER beta) present on ACL fibroblasts. Progesterone appears to play a protective role, partially counterbalancing the effects of estrogen; thus, the estrogen/progesterone ratio is often a more accurate predictor of laxity than isolated estrogen levels.
* Neuromuscular Impact: Hormonal fluctuations affect not only the ligament structure but also proprioception, reaction time, and muscle activation patterns (e.g., quadriceps dominance at the expense of the hamstrings).
* The Role of Relaxin: Although relaxin contributes to laxity, its role outside of pregnancy remains a subject of debate, with its impact considered secondary to the interaction between ovarian steroids.

CONCLUSION:
Modern prevention must integrate physiological monitoring to reduce injury rates. Recommended strategies include:
1. Menstrual Cycle Monitoring: Utilizing tracking apps and biomarkers to identify individual windows of vulnerability.
2. Periodized Neuromuscular Training: Intensifying stability, motor control, and hamstring strengthening exercises during high-risk (pre-ovulatory) phases.
3. Pharmacological Considerations: Discussing the potential of monophasic oral contraceptives to stabilize hormonal fluctuations and reduce joint laxity variability.
4. Education and Awareness: Informing athletes and technical staff about the hormonal impact on biomechanics.