Exercises for knees that crack when squatting focus on the muscles that support the knees. When these muscles are strong they are able to better absorb the pounding the joints experience. Since the cause of the cracking sound can come from a variety of damaging conditions ranging from early osteoarthritis to a knee cap that is misaligned, don't do any exercises that will overstress your knees. Do try to see a doctor for an exact diagnosis so you can prevent further damage to your joints.
Knee strengthening starts at the top of your leg. The hip abductors in your buttocks provide power and shock absorption for your knee. Strengthen the gluteus maximus, medius and minimus by doing side leg lifts, bridges and hip extensions. To do a hip extension, lie face-down on the floor and bend your arms for support with your palms face-down. Keep your left leg straight and raise it off the floor, then squeeze your buttocks. Hold the position a few seconds, then lower and repeat. Do two sets of 10 repetitions on each leg. Place a small pillow under your abs if your back feels stressed during this exercise.
The next muscles to strengthen for your cracking knees are the quadriceps. These four muscles are located in the front of your thigh and are responsible for keeping the knee cap on its track in the femur and for making leg extension possible. Strengthen your quads by doing leg lifts while lying on your back and while standing up and also doing contraction exercises. To do a contraction, lie face down on the floor and place a pool noodle or rolled towel beneath your left ankle. Push your left foot down toward the floor and try to keep your leg straight. Hold the contraction for a few seconds, then release and repeat. Do two sets of 10 contractions on each leg.
The hamstrings work in conjunction with your quadriceps. They are located in the back of your thigh. These three muscles pull your leg back when you bend your knee. Strengthen them with lying and standing hamstring curls and also with hamstring contractions. To do a contraction, sit on the floor with your legs straight out in front of you and flex your toes. Now push down on your legs. You should feel a burn in the back of your thighs. Squeeze the hamstrings for a few seconds, then release. Do three sets of five repetitions.
You have two muscles in your lower leg, the soleus and the gastrocnemius. They are both responsible for flexing your feet, but the gastrocnemius is connected to the knee and also helps with the knee's ability to bend. Strengthen your calf muscles with seated and standing calf raises, isometric contractions and calf raises on a step platform. To do a calf raise on a step platform, stand on top of the step and allow your heels to hang off the back edge of the step. Feel the stretch as the calves sink lower to the floor, then raise up on your toes for a few seconds, then slowly lower your heels and repeat the exercise. Do three sets of five repetitions.