Knock knees is the slang term used for "genu valgum" — an inward angle of the thighs when a squat is performed or while standing in a neutral position. This deformity is typically caused by weak abductor muscles, which are found on the outsides of the hips and thighs.
To correct this problem, do abductor-strengthening exercises. The muscles involved with abduction are the gluteus maximus, gluteus medius, gluteus minimus and tensor fascia lata.
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Read more: Yoga for Knock Knees
1. Side Lunges
Side lunges work your abductors, hamstrings and quadriceps.
HOW TO DO IT: Stand with your feet hip-width apart and your arms in front of your chest. In a steady motion, take a big step laterally to your left. When your foot comes to the ground, bend your knee, and push your butt backward.
When you feel a strong contraction on your hip and other thigh, stand up, bring your feet back together and repeat to the other side. Continue to go back and forth for 10 to 12 repetitions. If you want more resistance, hold a medicine ball in front of your chest.
2. Side Step-ups
Side step-ups require the use of a weight bench or chair.
HOW TO DO IT: Stand with your right side facing the bench and your arms in front of your chest. In a steady motion, place your right foot on the bench, press down and lift your body in the air.
When your right leg is straight, hold for a second, lower yourself and repeat. After doing 10 to 12 reps, switch sides. As with side lunges, hold a medicine ball for added resistance.
Read more: How to Run With Bow-Legged or Knock-Knees
3. Cable Abduction
Cable abductions work your outer thighs and hips with one side of a cable machine.
HOW TO DO IT: Attach an ankle cuff to a low setting, fasten it around your lower right leg and stand with your left shoulder facing the weight stack.
In a smooth, arcing motion, lift your foot off the floor and raise your leg laterally to your right as high as possible. Slowly lower and repeat. After doing 10 to 12 reps, switch sides.
4. Lying Abduction
Lying abduction is done from a side-lying position.
HOW TO DO IT; Lie on your right side with your legs stacked. In a steady motion, lift your left leg at a 45-degree angle to the floor and hold for a second.
Slowly lower your leg, repeat for 10 to 12 reps and switch sides. For added resistance, hold a dumbbell against your thigh when you raise your leg.
5. Wall Abductor Squeeze
Wall abductor squeezes require an exercise ball.
HOW TO DO IT: Stand with your left side facing the wall Bend your knee until your thigh is parallel to the floor. Place the ball between the wall and the outside of your left knee.
Steadily press into the ball with your outer left leg and hold for a full second. Slowly release the pressure and repeat. After doing 10 to 12 reps, switch sides.