You've probably heard that your glutes (aka ass) are important muscles. They directly influence hip position and when activated correctly they can help your body move in an ideal way for specific tasks.
The glutes are one of the muscle groups responsible for external (outward) rotation of the hip. External rotation is important because it increases torque in the hip. When you add this rotation it removes the slack within the joint making it very tight and stable.
The video shown at the bottom of this article demonstrates the differences in knee, ankle and foot position when the hip is either externally rotated or internally (inward) rotated.
As you can see when the hip is externally rotated it increases the torque and helps stabilise the lower leg. The most obvious change you'll notice is the difference in height of the arch around the mid foot. These changes are important for functional movement. Squats, running and jumping are good examples.
Why should we care?
The stability around the knee helps to prevent laxity in the ACL thus reduces risk of ACL tear when performing high impact movements.
The change in ankle/foot potion helps to increase ankle range of motion (specifically dorsiflexion) it reduces the risk of ankle injury from high impact and repetitive ankle movements.
When performed incorrectly as demonstrated with internal rotation of the hip there is a higher risk of anterior ankle impingement, development of bone spurs, and a range of knee injuries some of which include ACL tear, patella tendinopathy and patellofemoral pain.
Hopefully this helps you to understand why it is important for us to have good gluteal strength and activation. When in doubt you can't go wrong getting strong!