The Clamshell Exercise
I love this move because you can do it without equipment or you can add some bands to make it more challenging.
This exercise strengthens the gluteus medius, which controls rotation of the femur and alignment of the knee during running and walking. It is very important to keep this muscle strong and stretched properly.
To get started you will lie on your right side with your right arm extended with your head resting on the right arm. Bring your knees forward up to a slightly bent position in front of you. Your heels should be in line with you head and spine, and your hips are stacked on top of each other.
Now you will leave you right leg positioned on the floor and slowly raise your left leg still bent towards the ceiling. Your heels stay together as you move your upper leg up and down like the clamshell. Repeat 15-20 times for each leg. For added resistance you can add a circular band around just above the knees (lower thigh) as shown in video below.