Most of us know that a good way to protect our knees is to strengthen the muscle above the knees with simple quad exercises. But, for added support, it's also important to keep your hips and hamstrings flexible. Here's a side-lying stretch that targets your hips and hamstrings.
1) Lie on your side, legs straight, with your feet, hips and shoulder stacked. Rest your head in your hand (or place it down on your forearm with your elbow forward). Bend your left knee and place your left foot flat on the floor in front of your right knee. While maintaining your balance, use your left hand to gently press your left thigh back until your left knee points toward the ceiling. Resist rolling backward by keeping your left hip over your right hip.