 Hi everybody, Dr. O here. In this video I'm just going to cover your four quadriceps muscles, so if you've already been through the muscles of the thigh then really this is redundant, but if this is the first video you're finding and you're just looking at the quadriceps muscles this is a great place to start. So the quadriceps is not a muscle, it's a group of four muscles. So the quadriceps muscles are the rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius. So they all have the same function as far as knee extension goes, but the rectus femoris has an extra one. So rectus means straight, we'll start there. Rectus femoris, quadriceps muscle running straight from down in the middle. It's involved in knee extension, sorry, but because it crosses the hip it's also involved in hip flexion. The only one of your quadriceps muscles that does that, so that's your rectus femoris. Vastus medialis is on the inside of the thigh, so it's involved in the extension, but also a very important muscle because I've said this in other videos, but patellar tracking problems can be a real issue, especially in women or anyone with a broader pelvis because of the increased cue angle. The patella should run nearly up and down when you're walking or running. If it starts to track, pull to the outside, it actually can start to rub on the under surface of the patella and can cause a condition called chondromalacia patella or a softening of the cartilage under the patella. Leads can lead to some knee pain, popping and snapping and clicking inside the knee and then can lead to further issues down the line if it becomes damaged, basically arthritis there. So surgically they can do what's called a lateral release and they can cut some of the connect tissue on the outside of the knee, but I find that a conservative approach use you works better. So if you have this issue, you know, work with somebody, work with a physical therapist or someone that knows what they're doing, someone in sports medicine and strengthen the inside of your leg, the vastus medialis, especially the vastus medialis oblique fibers at the bottom. So relatively simple a thing to do. So rather than cutting the outside of the knee, strengthen the inside of the knee and see if you can't pull that patella back in place and get it and get it to track properly. So the vastus medialis is very important. It's not medical advice. I'm just saying something to consider. So that's the vastus medialis. On the outside, we have the vastus lateralis. So medial being on the medial side, lateralis being on the lateral side. Then in the middle, you can't see it here, but the vastus intermedius. If I were to take off the rectus femoris, right in the middle there would be the vastus intermedius. So all four of those muscles are involved in the extension, which I've said before is kind of odd because usually the flexors are on the front of the body, but the knees, the exception to that rule. And that's your quadriceps muscles. I hope this helps. Have a wonderful day. Be blessed.