The knee is the largest joint in the body. People use it heavily every day as they walk, run, climb, or jump. As a result, it is also very prone to injury and pain. When these occur, a doctor may recommend exercises to help a person strengthen the muscles around the knee.

People of all ages may experience knee pain. According to one article, a type of knee pain called patellofemoral pain syndrome, or runner's knee, is the most common orthopedic condition in sports medicine. In addition to being common in athletic people, knee pain can also be a problem for people who have arthritis.

While it may be tempting to avoid exercise when knee pain occurs, this is not always the appropriate solution. Certain types of exercise can help alleviate existing knee pain and prevent future pain or injury by providing the knee with extra support.

The Arthritis Foundation state that exercise may be the most effective way to treat osteoarthritis without surgery, while the American Academy of Orthopaedic Surgeons note that strong and flexible muscles can keep knees healthy and prevent injury.

Knee strengthening exercises do not affect the knee joint directly, but they strengthen the muscles surrounding it. Strong muscles in the legs can help provide support for the knees. This support may alleviate pressure and strain on these joints, which can relieve pain and help a person be more active.

The following exercises can help strengthen the muscles surrounding the knee. If a person experiences pain during these exercises, they should stop doing them and speak to a doctor. Anyone with severe knee pain should consult a doctor before trying to exercise.

It is best to warm up with light exercise before starting any knee strengthening exercises. Examples of gentle exercise include walking, cycling, and using an elliptical machine, all of which put minimal stress on the knees. This activity will help increase blood flow to the muscles and allow them to be more flexible.

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Muscles involved: Quadriceps (front of the thigh) and abdominal (stomach) muscles.

  1. Lie down on the floor with the back flat. Use a yoga mat, folded blanket, or exercise mat for comfort on a hard floor.
  2. Keep the left leg straight and bend the right leg slightly at the knee, bringing the foot closer to the body.
  3. Pull the abdominal muscles inward by imagining the belly button pulling down toward the floor. Doing this should bring the lower back down against the floor and help provide extra support during the exercise. Place a hand beneath the lower back to make sure that there is no space between the small of the back and the floor. If there is space for the hand, gently push the lower back down on top of the hand.
  4. Slowly lift the left leg without bending the knee. Keep the toes pointed toward the ceiling and stop when the leg is about 12 inches off the floor. It should not be higher than the bent knee on the right leg.
  5. Hold the left leg up for 5 seconds.
  6. Slowly lower the leg back down to the floor. Do not put it down too quickly or let it drop.
  7. Repeat two more times with the same leg.
  8. Switch sides and repeat.

What not to do

  • Do not let the back arch during the exercise.
  • Do not jerk or bounce the leg or lift it above the knee on the bent leg.
  • People who have osteoporosis or a back compression fracture should not perform this exercise.

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Muscles involved: Hamstrings (back of the thigh) and gluteal (buttock) muscles.

  1. Stand straight with the knees only 1–2 inches apart. Hold on to a stable chair, the countertop, or another object for balance.
  2. Slowly bend one knee behind the body, lifting the heel off the floor while keeping the thighs aligned. Continue to lift the heel in a smooth motion until the knee bend reaches a 90-degree angle. Keep the straight leg slightly bent to avoid locking it.
  3. Hold the bent leg up for 5 seconds and then slowly lower it to the floor.
  4. Repeat two more times with the same leg.
  5. Switch sides and repeat.

What not to do

  • Do not point the toes or flex the foot on the lifted leg. Allow the foot to remain in a neutral, flat position.

Muscles involved: Hamstrings and gluteal muscles.

This exercise is a variation of the standing hamstring curl. A person can try this version if they have access to a weight bench that is purpose-built for this exercise. It may be more challenging than the standing hamstring curl, depending on how much weight a person uses.

  1. Lie face down on the bench with the knees close together. Grip the handles for stability.
  2. Tuck the feet under the weight. The weight should sit just above the heels.
  3. Slowly bend both knees, using the force of the legs to raise the weight up. Continue to lift the weight in a smooth motion until the knees bend at a 90-degree angle.
  4. Hold the weight up for 5 seconds and then slowly lower it back down.
  5. Perform up to 15 repetitions (reps).

What not to do

  • When first attempting this exercise, do not use a heavy weight. Beginners should use the lowest weight and work their way up to heavier weights as they build strength.

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Muscles involved: Quadriceps, hamstrings, hip flexors, and gluteal muscles.

  1. Use a large, sturdy stool or exercise platform no taller than 6 inches.
  2. Step up onto the stool with the right foot and allow the left foot to follow behind. The left foot should not be on the stool but should hang behind it.
  3. Keep the body weight on the right foot and hold for up to 5 seconds.
  4. Slowly lower the left foot down and then follow it with the right foot.
  5. Switch legs, stepping up with the left foot first.
  6. Repeat.

What not to do:

  • Do not lock the knees during this exercise. The knees should remain slightly bent.
  • Do not allow any part of the stepping foot to hang off the stool or platform.
  • People who have issues with balance should not perform this exercise.

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Muscles involved: Quadriceps, hamstrings, hip flexors, and gluteal muscles.

  1. Use two high-backed, stable chairs, placing one on either side of the body with the chair backs next to the arms. Place a hand on the back of each chair for balance.
  2. Bend both legs at the knee, being careful not to let the knees extend past the toes.
  3. Extend the right leg out in front of the body in a slow kicking motion. Focus on keeping the weight balanced on the left foot.
  4. Bring the right leg down slightly, holding it just a few inches off the floor for 5 seconds while continuing to balance on the left leg.
  5. Slowly lower the right leg completely to the floor.
  6. Stand up straight on both feet.
  7. Switch sides and repeat.

What not to do:

  • Do not bring the leg up more than 45 degrees off the floor.
  • Do not lean backward when lifting the leg. Keep the back and upper body straight.

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Muscles involved: Quadriceps and gluteal muscles.

  1. Stand with the head, shoulders, back, and hips flat against a wall.
  2. Step both feet out about 24 inches away from the wall, while keeping the back and shoulders against it. Keep the feet no more than hip width apart.
  3. Slide the back down the wall slowly until the body is just above a normal sitting position.
  4. Hold for 5 seconds and then slide back up.
  5. Repeat.

What not to do:

  • Do not squat too low. The knees should not go over the toes.
  • Do not use fast, jerky movements. Perform the exercise slowly and smoothly.

After exercising any muscle group, it is essential to stretch the muscles. Stretching helps improve flexibility and reduce pain and injury.

Quadricep stretch

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  1. Hold on to the back of a chair or put one hand on a wall for balance.
  2. Lift one foot behind the body and grab the ankle with the hand.
  3. Keep the back straight and the knees close together.
  4. Pull the heel close to the buttocks without forcing it or causing pain.
  5. Hold for up to 30 seconds and then slowly lower the leg.
  6. Switch sides and repeat.

Toe touches

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There are many different ways to stretch the hamstrings in the back of the legs. One is through traditional toe touching.

  • With the feet close together, slowly bend over at the hips and extend the arms downward. Keep the legs straight but do not lock the knees.
  • Reach the fingers to the top of the toes and hold for 30 seconds.
  • Initially, it may not be possible to reach the toes. In this case, try to get the fingers as close as possible to the toes without causing pain.

What not to do:

  • Do not use a bouncing motion. Hold the body still.

Standing hamstring stretch

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A standing hamstring stretch is also an effective way to stretch the backs of the legs, and it is less strenuous for the lower back than toe touches.

  1. Stand up straight with the feet no more than shoulder width apart.
  2. Bend at the hips slightly and extend the right leg out a few inches in front of the body. Allow the left leg to bend slightly.
  3. While keeping the back straight, slowly bring the chest downward.
  4. Bend down as far as possible without causing pain. Hold for 30 seconds.
  5. Slowly bring the leg back toward the body and stand up straight.
  6. Repeat with the other leg.

Exercise is a noninvasive and healthful way to help with minor knee pain due to overuse, arthritis, or other causes.

Knee strengthening exercises are an effective way to help prevent injury and keep the legs strong. Stretching can also help keep the muscles flexible, which can prevent or alleviate pain.

People who have health conditions should speak with a doctor before beginning any exercise program.