DOES HIP MUSCLE STRENGTH INFLUENCE THE DEGREE OF LOWER LIMB VALGUS ROTATION IN YOUNG FEMALES?

Abstract

Background: Female athletes are suffering more injuries to the knees than male athletes and this can be due to lower limb alignment issues. If the biomechanics of the lower limb are altered then certain anatomical structures, such as ligaments, may be highly stressed during dynamic tasks. It is thought that weak hip musculature can be a cause of valgus rotation, leading to uncontrolled collapsing of the knee. Excessive valgus knee rotation during landing places knee structures, particularly the anterior cruciate ligament (ACL), under high stress which can result in injury. Aim: The aims of this study were two-fold 1) to observe if isometric hip strength was related to lower limb alignment measurements and 2) to examine the reliability and comparability of 2D video analysis and lower limb alignment measurement techniques. Methods: This was carried out with 2D video analysis observing the subjects whilst they performed single-leg and double leg squats. The subjects then had their hip strength tested (abductors, extensors and external rotators) using a hand-held dynamometer. Once the data was collected SiliconCOACH was used to analysis the squatting performance. The amount of valgus (degrees), Q-angle (degrees), hip to knee distance (cm) and standing knee to squatting knee distance (cm) was recorded during the single-leg and double-leg squats on both dominant and non-dominant leg. Fifteen female students, all physically active and injury free, took part in the study. The mean (SD) for age = 20.3±0.7 years, height = 164.9±4.6 cm and mass = 62.9±5.7 kg. Results & Discussion: Results showed that hip strength does influence and decrease the degree of valgus knee in young females; particularly relating to the hip external rotators. Valgus knee angle was found to be greater whilst single-leg squatting in subjects where the external rotator muscles were relatively weak. Further research is required, however, the moderate to strong correlations (non-dominant r = -0.48, dominant r = -0.59) between knee valgus angle and external rotator muscle strength indicate that prehabilitation programmes aimed at strengthening this muscle group may improve dynamic lower limb knee alignment in active young females and this in return might protect against knee injury.