Author(s): JONES, K., HERRINGTON, L., Institution: UNIVERSITY OF GLOUCESTERSHIRE, Country: UNITED KINGDOM, Abstract-ID: 528

INTRODUCTION:
Anterior cruciate ligament (ACL) injuries remain a concern for female athletes, with joint laxity and proprioception identified as potential contributing factors. Hormonal fluctuations across the menstrual cycle (MC) have been proposed to influence these parameters; however, findings remain inconsistent (Oester et al., 2024). This study investigated the effects of MC phase on knee joint laxity and stiffness, and the relationship between laxity and joint position sense (JPS).
METHODS:
Eleven eumenorrheic females (21 ± 5 years) completed a repeated-measures study. Anterior knee laxity was assessed as anterior tibial translation using a GNRB® arthrometer (D Max, ICC = 0.82, SEM = 0.26 mm). Knee joint position sense (JPS) was evaluated via active angle reproduction at 30° and 60° of knee flexion using an iPhone-based inclinometer application, with proprioceptive error expressed as joint angle error (JAE; ICCs = 0.48 and 0.99, respectively). Menstrual phase was classified retrospectively using self-reported tracking and urinary luteinizing hormone (LH) testing. MANCOVA assessed phase variation in laxity and stiffness. JAE variation across phases was analysed using Friedman’s test, with Wilcoxon Signed-Rank tests comparing 30° and 60°. Spearman’s correlation examined associations between D Max and JAE with statistical significance set at p < 0.05 and Bonferroni correction applied.
RESULTS:
No statistically significant group-level differences were observed in joint laxity, stiffness, or JAE across MC phases (p > 0.05). However, individual responses varied considerably. Some participants demonstrated marked increases in joint laxity during ovulation, while others remained relatively consistent across the cycle. A large phase-specific association was identified between knee laxity and JAE at 60° during ovulation (r = 0.62), suggesting increased proprioceptive demand at deeper knee flexion angles when ligamentous support may be reduced.
CONCLUSION:
These findings highlight the limitations of group-mean reporting in menstrual cycle (MC) research, particularly in team-based sport contexts where individual responses to hormonal fluctuations may differ substantially. While phase-based effects were not evident at a population level, meaningful individual variability may still exist. This supports a shift toward more individualised, context-aware approaches, potentially incorporating symptom-based monitoring alongside phase classification.