Sex Hormones Explain More Variance In Anterior Knee Laxity Across The Menstrual Cycle When A Time Delay Is Considered

Abstract

0258 PURPOSE: To determine the relationship between daily changes in anterior knee joint laxity and sex-hormone levels across one complete menstrual cycle, with and without a time delay considered. METHODS: 22 females (23.0±3.5 yrs, 163.4±5.6cm, 65.0±11.6 kg, 24.3±3.5 BMI) who reported normal menstrual cycles (28–32 days) were tested daily across one complete cycle. Serum levels of estradiol (pg/mL), progesterone (ng/mL), and testosterone (ng/mL) were assayed. Knee laxity was measured with a standard knee arthrometer, and the displacement (mm) obtained at 133N was used for statistical analysis. A multiple linear regression model with the possibility of a time delay (range 0–8 days) was performed on individual subjects, and the group as a whole. RESULTS: Individual regression equations revealed that, on average, 63.3±7.7% of the variance in knee laxity was explained by the three sex hormones and their interactions when a time delay was considered. The strongest relationship was noted when knee laxity changed approximately 3.1±2.3, 3.9±2.9 and 4.5±2.4 days following changes in estradiol, progesterone and testosterone respectively. This model explained substantially more variance in knee laxity than when no time delay was allowed (25.9+15.8%), and when only estradiol (18.6+10.1%) or estradiol + progesterone and their interaction (36.7+12.5%) were entered in the model with a time delay. When females were analyzed as a group, sex-hormone levels explained only 8% of the variance in knee laxity. CONCLUSIONS: Estradiol, progesterone and testosterone each contributed to changes in knee laxity across the cycle, with this relationship strengthened at some time delay. However, consistent with the variability in menstrual cycle characteristics between females, the strength of this relationship, the relative contribution of each hormone, and the associated time delay were also variable between females. Supported by NIH Grants RO3 AR47178 and MO1 RR00847, and through a cooperative agreement [U54 HD28934] as part of the Specialize Cooperative Centers Program in Reproductive Research.