Your knee joints are a hinge-style joint, and are meant to bend and straighten in one direction. There are many muscles around the knee that create force and exert pull on the knee joint. These forces and pulls can move the knee out of its intended movement path, which can create pain and injury. You can improve knee alignment by performing exercises that strengthen the surrounding muscles and train the knees how to move.
The first exercise you should try is the assisted squat. You will need a small, slightly soft playground ball, approximately 6 inches in diameter. Place the ball between your thighs just above the knees. Stand with your feet 4 inches apart and toes facing forward. To begin your squat, simultaneously bend your knees and hips and push your tailbone back as if you were going to sit down into a chair. Go as low as you can, keeping your heels on the ground and your chest slightly lifted, and then stand back up. Throughout this movement, keep the ball in place by gently squeezing your thighs into the ball. Perform this assisted squat 15 to 20 times.
The bridge exercise is an effective knee-aligning movement as it strengthens the hamstrings and glutes--the back of the thighs and buttocks--which help move the knee in its intended path. To set up for this exercise, lie on your back with your knees bent and feet flat on the floor. Place the small playground ball between your thighs, just above the knee. With your arms on the floor by your sides, press into your feet and lift your hips and back of the floor. Squeeze into the ball and squeeze your glute muscles as you lift and lower back down to the floor. When you are in the lifted position your torso will be resting between your shoulder blades. Perform 15 to 20 repetitions of the bridge.
Quad sets strengthen the quadricep muscles, which are the front of your thighs and are important muscles in knee movement. Sit up tall in a chair with your feet flat on the ground. Your legs can be 2 to 3 inches apart. Tighten your thighs as if you are trying to firm all the flesh of your upper legs in toward the thigh bone. Hold this contraction for the count of five, then release and repeat 15 to 20 times.
A second variation of this exercise is slightly more advanced and has some additional strengthening benefits. In the same starting position, straighten your legs out in front of you as your thigh muscles get firm. Again, hold this for the count of five and then release your feet back to the floor.