Our legs allow us to do everything from walking to dancing to just standing still. All these actions involve the function of many muscles. Learn about the muscles above the knee in this lesson covering muscles of the hip, thigh, and leg.
The Pelvic Girdle
So, how many of you are runners? Or, who likes dancing, playing football, or maybe soccer? What do all of these sports have in common? Not sure? Well, it's a lot simpler than you might think. They all involve the use of your legs! The muscles of your legs are called appendicular muscles because they are attached to the bones of the appendicular skeleton. This attachment site is called the pelvic girdle, these bones here, which are attached to the axial skeleton here at the sacrum.
On top of the pelvic bones are muscles that move the hips, or pelvis. These movements consist mostly of rotation of the hips, side-to-side movement, or back-and-forth movements and are often paired with movements of the thigh or upper part of the leg. All of the muscles that move your legs can be divided into three groups: muscles that move the thigh, muscles that move the leg, and muscles that move the foot and toes. We'll start at the top, with the muscles that move the hip and thigh, and focus on the muscles above the knee in this lesson.
Muscles That Move the Hip and Thigh
First up: the gluteus maximus, or your butt muscle. This muscle is the largest and most well-known of the gluteal group of muscles, which includes the gluteus medius, maximus, and minimus, as well as the tensor fasciae latae. Together, these muscles extend, flex, and rotate the hip. The origin points for these muscles are on the posterior side of the illium of the pelvic bone, this part here. Some, like the gluteus maximus, have multiple origin points and also originate from the sacrum and coccyx, these bones here.
These muscles all insert either on the femur, the large bone of the upper leg, or the iliotibial tract. This is a tract of collagen fibers that extends from the hip along the thigh and down to the tibia of the lower leg, inserting just below the knee. This IT band, as it is commonly called, helps support the knee and flex, abduct, and rotate the thigh at the hip joint. Remember, abduction is the movement of a part of the body away from the center of the body, while adduction is movement toward the center of the body.
I know these terms are easy to confuse, but if you think about it, what does the word 'abduct' mean? If somebody is abducted by aliens, they are taken away from Earth, right? So 'abduction' equals 'away from,' while 'adduction' equals 'adding to' or 'bringing back towards' the body. Not so hard to remember now, right?
Underneath the gluteal muscles are other muscles involved in movement of the hip and thigh, the lateral rotator group, which, as its name suggests, rotates the hip laterally, away from the body, like this. Below this group are the adductors, which move the hip back toward the body. All of the adductor muscles, as their name suggests, perform hip adduction, and some also perform flexion and extension of the hip. Whenever someone suffers from a pulled groin, it's usually because one of these muscles has been injured.
Muscles That Move the Leg
Underneath the hip and thigh are the muscles that move the leg. These can be divided into muscles that flex the leg and those that extend the leg. This flexion and extension occurs at the knee. Most of the muscles involved in flexion of the knee and leg are located along the back (or posterior) and side surfaces of the leg.
These muscles include the biceps femoris. Hmm, that 'biceps' term sounds familiar, doesn't it? That's right; doesn't the biceps brachii flex the arm? Well, the biceps femoris flexes the leg at the knee. This can pull the lower leg up or move the entire leg back, away from the body. This motion is aided by other flexors, and together, they are referred to as the hamstrings. The hamstring muscles originate up here at the pelvic bone and insert down here on the tibia and fibula of the lower leg.
The hamstrings are the opposing muscles, or antagonists, to the quadriceps muscles located on the front, or ventral, side of the leg. When the quads contract to extend your knee, they pull your leg up and allow you to move it away from your body. In this way, they are the prime mover, or the agonist. When the hamstrings contract, they pull the leg back, toward your body. You can see this action most easily when you're walking or running.
The quadriceps are made up of four knee extensor muscles, which extend the lower leg at the knee. They push the leg forward, away from the body. All except the rectus femoris originate up here along the femur bone of the upper leg and insert down at the patella, or the knee cap. The rectus actually originates further up at the iliac spine of the pelvic bone but still inserts down at the patella.
And those are just the leg muscles above the knee! We haven't even gotten to muscles below the knee yet. But don't worry, they have a lesson all their own! For now, let's run through a quick review of the leg muscles above the knee.
The muscles of the lower limbs, or legs, are considered to be appendicular muscles because they are attached to the bones of the appendicular skeleton. Both the muscles and bones of the legs are attached to the axial skeleton via the pelvic girdle.
On top of the pelvic girdle are muscles that move the hips and thighs. The main muscles responsible for this movement belong to the gluteal group. Underneath the gluteal group are muscles of the lateral group. These muscles control the lateral rotation of the hip, moving it away from the body. Opposing these muscles are adductors of the hip and thigh. Adductor muscles move the hip and thigh back toward the body through medial rotation, flexion, and extension.
On the outer surface of the upper leg we also have the iliotibial band ,or the IT band. The main function of this band of collagen fibers is to help support the knee and abduct and rotate the thigh. On either side of the IT band are leg flexors and extensors.
These muscles, located on the back and front of your thigh, are commonly called the hams and quads. These are the primary muscles used in actions, like walking and running, which require flexion and extension at the knee joint. The quadriceps are located above the knee on the front of your leg. They help extend the leg away from your body and can also pull your leg upward, as you can see in these exercises.
Opposing your quads are their antagonists, the hamstrings, which flex the leg at the knee, moving it towards the body as seen in these exercises. The main flexor muscle of the hamstrings is the biceps femoris. And if you've seen our lesson on the muscles of the arms, you may have noticed some similarity in organization. Just like the arms, the majority of the extensor muscles are located on the dorsal side (this side here) with the knee cap, while the flexor muscles are located on the ventral side, or the back of the leg.
And that's it, some of the main muscles of the legs - well, those located above the knee, anyhow. For the muscles located below the knee, be sure to watch our other lessons on muscle anatomy.
After the conclusion of the lesson, you should be able to:
- Detail the function of the upper leg
- Describe the muscles of the hip and thigh
- Understand the major muscles of the upper leg to the knee