The knee functions as a hinge for bending and straightening the leg, and allows us to twist and turn as we move. As such, it is highly vulnerable to injury, strain and overuse. Strengthening the muscles around the knee can help to protect the joint, decreasing the possibility of pain, stiffness and overall vulnerability. Exercise can increase your range of motion and ease daily living activities. Following are some ideas for knee strengthening exercises, but proceed with caution. If you experience any pain whatsoever while performing these exercises, stop immediately and seek medical attention. If you are under a doctor's care consult him/her before starting this exercise regimen.

Leg Extensions: This exercise strengthens the inner thigh muscle to help balance the pull on the knee joint from the outer thigh, which is usually stronger.

1. Sit against a straight back chair.
2. Straighten one leg and hold for one minute, then slowly lower it down
3. Bend your knee and lower halfway back to the floor. Hold for 30 seconds
4. Return foot to the floor and rest
5. Repeat and work up to five repetitions per leg.
6. Increase resistance by adding ankle weights over time

Straight Leg Raises: This exercise strengthens the thigh muscles to help support the knee joint.

1. Sit on the floor against a wall with your legs straight in front of you and your toes pointing upward.
2. Lift one foot off the ground while keeping the leg straight and hold for 10 seconds, then slowly lower it back to the ground.
3. After a momentary rest, repeat.
4. Work up to 3 one minute holds per leg.

Step-Ups: This exercise helps to strengthen thigh muscles just over the top of the knee joint.

1. Stand in front of a bench or stairs, some type of surface that's about two feet off the ground.
2. Step up with both feet and straighten your knees, then step down.
3. Repeat at a steady pace. Work up to 25 times.