Deadlifts are easy on the knees if you keep them held primarily straight.
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Common exercises that target your major butt muscle also require contribution from your knee joints. However, there are a handful of butt exercises that you can incorporate into your workouts that take it easy on the knees. To ensure your lower-body muscles are warm and ready for exercise, go for a walk or ride a stationary bike for five to 10-minutes before beginning the butt exercises.
The Butt Muscle
The major muscle of your butt is your gluteus maximus, which originates at your pelvis and then runs to the side of each leg, where it attached at the outside of your upper femur bone. Your gluteus maximus is responsible for driving your upper leg back behind you. When you come up out of a squat or lunge, your gluteus maximus is moving your leg backward, or extending your hips. However, these exercises require movement at your knees. Glute exercises like standing cable hip extension, reverse hyperextension and stiff leg deadlift, which take the knees out of the equation, focus solely on moving the upper legs backward.
Standing Cable Hip Extension
The standing cable hip extension exercise can be performed with a cable pulley unit. Set the unit so that it's placed at its lowest position. Attach the strap at the end of the cable to one of your ankles. Stand facing the unit with all your weight on your free leg. Keep your knee straight as you pull your attached leg back behind you as far as you can while keeping your torso erect. Control your leg back down and then repeat. After you're done with the set, work the other leg. You can also perform the standing hip extension with an exercise band.
The reverse hyperextension requires the use of a bench or hyperextension apparatus. Lie face down on the bench and hold the end with both hands. Your legs, from the waist down, should hang off the edge. Begin with your legs pointed toward the floor. Keeping your knees straight, lift both legs up until they're in line with your torso and then lower them back down to finish the rep. Wear ankle weights or squeeze a medicine ball between your feet to increase resistance.
Stiff Leg Deadlift
An advanced exercise for targeting the glutes are stiff leg deadlifts, which require the use of a weighted barbell. Hold a barbell down in front of your thighs, with your hands just wider than your hips and your palms facing your thighs. Set your feet to shoulder-width with toes pointed forward. Keep your knees primarily straight, but not locked, as you bend forward at the waist, lowering the bar toward the top of your feet. Continue until your back is about parallel to the floor and then extend your hips to return to a standing position.