Tight quads (which is the front of your leg and the muscles that are in that area) can cause pain in more than one area. You can put pressure on your knees, hips and can get trigger points and soft tissue problems through the quadriceps. There are a few ways to release your quads, but the easiest way that anyone can do is to stretch.
Your quad consists of three muscles you are concerned about when stretching (there are actually four but the VMO is not so easy to stretch). Your rectus femoris muscle, which is the one that crosses both the knee and the hip joint, it is long and thin and extends the knee as well as flexes the hip. The vastus medialis and lateralis are on the inner and the outer of the thigh respectively. These only cross the knee joint and are knee extensors, they don’t cross the hip.
There are many different ways of stretching tight quadriceps, but here are a couple of examples to really get you a good, tough stretch. be sure to hold the stretch for at least 30 seconds, you might be able to get a better fascial stretch that way. the fascia is the sheath of connective tissue that surrounds all the muscles, and can get tight in itself.