A couple of years ago I went through a severe issue which was deterring and painful alike. I was running 4 times a week, trying to squeeze in some yoga and strength training in between but my knee gave me tremendous discomfort and pain despite my attempts to alleviate it.
I realized only then how important it is to strengthen and stretch the four-muscle group.
These few yoga postures did help me a lot to strengthen the muscles and I am ever since knee pain free.
What you need: Block, Strap, Mat
Supta padungushtasnana(need a strap) This posture is not only beneficial for knee pain but also general health of stretching hamstrings. It helps relieve lower back pain to some extent. Methodology- lie down on the back and bend one knee at a time. Hook the strap around the ball of your foot and straighten the leg up towards the ceiling. Hold for 10-15 breaths and change sides.
Bridge pose/Setubandhasana(need a block)This is a great pose to strengthen and soothe knee pain. It also helps strengthen the hamstrings and lower back. Methodology- Bend the knees and set your feet hip width apart. Place a block between the thighs and bring attention to the inner thighs and hamstrings .When we regularly strengthen these areas ,our knees, pelvis and muscles are engaged which helps releasing knee pain.
Mountain pose/tadasana (with block) One of the most simple looking yet very effective pose. In this pose we focus our attention on activation of muscles. Methodology- Feeling the four corners of the feet, grounding the feet towards the mat and then gently pulling the knee cap up. Fire up your legs feeling the inner thighs,quads and hamstrings.
Utkatasana/Chair pose (with block) Another great way to strengthen glutes and quads is chair pose.It works wonders to strengthen your legs and glutes. Methodology- Emphasize on putting weight towards heels and squat down like you are sitting on a chair. With the block in between the thighs, fire up the inner thighs, quads and hamstrings. Make sure the knees do not extend over your toes and maintain a neutral spine without hyperextending your back.
You will find this useful in practice, and feel stronger in your legs and knees.