Strong knees are important for athletes and non-athletes alike. Your knees are supported primarily by your quadriceps and hamstrings, but your calf muscles and hip adductors and abductors also play a role in knee stability. Strengthening these muscles is a critical part of protecting your knees from injury and pain. If you already have knee pain or injury and are unable to support yourself while exercising, there are several knee-strengthening exercises that can be performed while sitting in a chair.
Leg extensions work your quadriceps muscles located on the front of your thigh. Sit in a chair with your knees bent and feet flat on the floor. Lift your right foot off the floor by straightening your knee. Pause at the top of the movement, squeezing your quads. Lower your foot back to the floor and repeat the extension with your left leg. Perform one to three sets of 10 to 15 repetitions per leg.
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The hamstring contraction strengthens your hamstring muscles with an isometric contraction. Sit in a chair with your knees bent and feet flat on the floor. Straighten your right leg slightly and lift the toes of your right foot so that only your heel remains on the floor. Contract your hamstring muscles and press your heel into the floor. Hold this contraction for five to 10 seconds, without moving your foot. Repeat the exercise with your left leg. Complete the hamstring contraction three to five times with each leg.
The hip adduction exercise strengthens your adductor muscles on your inner thighs. Sit in a chair with your knees bent, feet flat on the floor and together. Make a fist and place it between your knees. Squeeze your knees together by contracting your adductors. Hold the squeeze for 10 seconds and then relax. Complete one to three sets of 10 reps of this exercise. You can substitute a tennis ball or volleyball for your fist, allowing you to squeeze harder.
The hip abduction exercise targets your gluteus medius, gluteus minimus, sartorius, and tensor fascia latae muscles that work to draw your leg away from your body. Sit in a chair with your knees bent, feet flat on the floor and legs together. Maintaining this position, secure a resistance band around your legs just above your knees so that the band is tight. Slowly press your knees apart as far as you can, working against the resistance of the band, and then return to the starting position. Complete one to three sets of 10 reps of the exercise.
The heel raise exercise strengthens the triceps surae muscles of your calf. Sit in a chair with your knees bent and feet flat on the floor. Place your hands on your knees. Slowly lift your heels off the floor while simultaneously pressing down on your knees with your hands. Lift as high as possible, pause and squeeze your calf muscles, then lower your heels back to the floor. Perform one to three sets of 10 reps of the heel raise.