There are some reports that increased adductor muscle activity may be related to the display of knee valgus during certain movements, including bilateral squats (Padua et al. 2012) and unilateral squats (Mauntel et al. 2013). (strengthandconditioningresearch.com)
However, the contribution of gluteus maximus force production and neuromuscular activity to knee valgus during normal movement remains unclear. (strengthandconditioningresearch.com)
The most common reasons for knee valgus include insufficient ankle dorsiflexion range of motion, poor hip mobility, poor gluteal strength and development and muscle poor coordination in the lower body in general. (fitnessandpower.com)