The gluteus maximus, which typically is referred to as the butt or glutes, is a large, powerful muscle exercised through squats and lunges -- compound exercises that engage the knee joint and hips. If you suffer from knee pain or injury you can still effectively strengthen your butt without bending or impacting the knee joint. Glute exercises that do not incorporate the knee are performed by keeping the legs straight and are executed in a standing or lying position.
Standing Hip Extension
Using a chair for balance, stand straight with your hands on the back of the chair. Exhale and slowly lift one leg behind you -- extending the hip -- while squeezing in your glutes. Lift as high as your flexibility will safely allow and then slowly lower your leg as you inhale, remembering to keep your leg straight. Repeat at least 10 times and then continue the same exercise with your opposite leg. You can make this exercise more difficult by wearing ankle weights or strapping your ankle to a weighted cable at a gym.
Begin by placing a barbell behind your neck with your hands on each side. Keep your back straight, exhale, and slowly bend your hips forward until your torso is parallel to the floor. Do not lower yourself beyond a mild stretch in the hamstrings. Keep your legs straight, inhale and slowly raise your torso back up to a standing position. It is best to begin this exercise with very little weight in order to allow safe adaptation of your glutes and hamstrings -- the assisting muscles in this exercise.
Single Stiff-Leg Deadlift
Stand with your feet together and your hands in front of your thighs. Lift one leg so that your foot is just off the floor, exhale and bend forward while keeping your back straight and your stomach in tight. As you bend forward, keep your extended leg straight. Your supporting leg may bend slightly if your are less flexible. Once you feel a stretch in your extended leg and your hands are close to the floor, inhale and slowly return back to your standing position. Repeat this at least 10 times before switching to your opposite leg. Holding dumbbells will make this exercise more difficult.
Prone Hip Extension Using a Stability Ball
Using a stability ball, lie in the prone position -- face down -- on your ball and place your hands on the floor with your elbows bent. You can lightly press your elbows into the ball for extra stability. Start with your legs straight and your toes on the floor. Your neck should be in line with your body and your head should face down a few inches from the floor. Exhale as you lift your feet off the floor -- keeping your legs straight -- and up toward the ceiling. Lift your legs slowly until they are in line with your spine and then inhale and lower your feet back toward the floor.