Association of estradiol and progesterone with knee anterior cruciate ligament injury factors: Ligament laxity, skeletal muscle strength, and tendon extensibility

Date of Completion

January 2007


Health Sciences, Rehabilitation and Therapy|Health Sciences, Recreation|Biology, Physiology




Anterior cruciate ligament laxity, knee extension strength, knee flexion strength, hand grip strength, ankle dorsiflexion-tendon extensibility, serum estradiol, and serum progesterone were measured 12 times across the eumenorrheic ovulatory menstrual cycles of 24 moderately active participants with the following characteristics: mean age 29 ± 4.7 years; mean BMI 22.9 ± 2.6, mean menstrual cycle length 29 ± 2.4 days. All subjects scored 100 on the Modified Lysholm Knee Scale and at least 6 on the Tegner Activity Scale. There were 17 White, 2 Black, 2 Hispanic, and 3 Asian participants. The sample means were: anterior cruciate ligament laxity 40.93 ± 21.69 N/mm, knee extension strength 91.03 ±24.74 pounds, knee flexion strength 37.15 ± 11.32 pounds, hand grip strength 71.25 ±12.45 pounds, and ankle dorsiflexion 106.57 ± 6.38 degrees. A hierarchical model linear model analysis was performed to account for different cycle lengths and measurement times and to allow for missing data points. Predictive equations were developed for the ligament laxity, strength variables and tendon extensibility. The tendon extensibility equations contained no significant predictors. Progesterone was a significant level one model variable for ligament laxity and flexion strength. Estradiol was a significant level one model variable for extension and grip strength. All models included maximum estradiol as a level 2 predictor. The extension strength model also included the range of progesterone (maximum less the minimum) and maximum progesterone. The grip strength model also included the maximum progesterone. Further analysis of variance revealed there were no differences in ligament laxity, any skeletal muscle strength measure, or tendon extensibility among low estradiol high progesterone, high estradiol low progesterone, or low estradiol high progesterone participant conditions measured or for the outcome variables with predictive equations.^