Following are few exercises to reduce knee pain and strengthen them:
Flexing knees: Sit on a chair and loop a long towel under the foot. Gently pull the towel with both hands to bend the knee. Raise your foot 5 inches off the floor and hold it for 5-10 seconds. Release slowly and repeat 5 times on each leg.
Hamstrings: Stand and put one leg in front with toes straight up. With support form a chair or your back, bend another knee and hip until the hamstrings stretch. Hold for 5-10 seconds and then release. Repeat 5 times on each leg.
Push up knees: Place the left foot on the left platform or step or the bottom step of the staircase and push up a few inches on the left leg. The right foot should be straight and few inches off the floor and you should feel a stretch on the right thigh. Keep for 30-40 seconds and repeat the push up on each leg and do 2 sets.
Lifts: To reduce knee pain take a cloth piece ands attach it to the foot. Tighten the cloth under the left foot and pull up the right leg till the cloth stretches. Hold it for 10 seconds and then repeat it 7-10 times in each leg.
Do these knee exercises and reduce knee pain before it increases.