Thigh Muscles: Anatomy, Support & Movement

Lesson Transcript
Instructor: John Simmons

John has taught college science courses face-to-face and online since 1994 and has a doctorate in physiology.

Did you know the thigh is the part of the lower appendage proximal to the knee? The muscles of the thigh move the leg at the knee. This lesson will identify the major muscles involved in flexion and extension of the leg at the knee, including the hamstrings and quadriceps femoris groups. Updated: 01/15/2020

Thigh Muscles

I grew up playing backyard football. It was great fun and certainly a lot of exercise. Every now and then, my buddy would pull the ball away just as I was about to kick it. Sound familiar? I would get mad and everyone would laugh as I fell on my backside. Among others, we will discuss the muscles used to kick that football in this lesson.

The two groups of the large thigh muscles
Thigh Muscle Types

It is anatomically correct to refer to that part of the lower appendage proximal to the knee as the thigh and distal to the knee as the leg. In general, muscles located in the hip region will move the thigh, and muscles located in the thigh will move the leg. Most of the thigh muscles are contained within two large groups of muscles referred to as the quads, which extend the leg at the knee and the hamstrings, which flex the leg at the knee. These muscles are innervated by the sciatic, femoral, and tibial nerves. Sciatica is a condition resulting from compression of the sciatic nerve. A person experiences lower back pain, leg pain, and leg weakness in association with sciatica.

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  • 0:06 Thigh Muscles
  • 1:19 Leg Flexors
  • 3:26 Leg Extensors
  • 5:10 Lesson Summary
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Leg Flexors

We did what we called butt kicks in track practice to get faster. This exercise required us to flex our legs so our heels would actually kick our buttocks.

The semitendinosus is medial to the biceps femoris.

Let's start with the hamstrings group. The hamstrings group is composed of three muscles, all of which produce flexion of the leg. These muscles are located in the posterior compartment of the thigh, which is the back side. The biceps femoris is a double-headed muscle, hence the prefix bi. The long head originates from the pelvic girdle, while the short head originates from the femur. Both heads insert on the fibula and tibia of the leg.

If we look medial to the biceps femoris, we can see what we call the semitendinosus, which originates from the posterior pelvic girdle and inserts on the tibia. Deep to the semitendinosus, we can see the semimembranosus, which originates from the pelvic girdle and inserts on the tibia as well. Here's a hint to help remember the names: the semimembranosus is broad like a membrane, while the semitendinosus is narrow like a tendon.

The anterior location of the sartorius muscle in the thigh
Satorius Muscle

In addition to the three hamstrings, which we just talked about, the sartorius muscle helps to flex the leg as well. The sartorius is unique in that it is located on the anterior surface of the thigh, as opposed to the back side. This muscle originates from the anterior-superior iliac spine, runs at an angle across the thigh and inserts on the medial surface of the tibia. Now, what about this anterior-superior iliac spine? You can actually feel it if you take your thumb and press it up against the front side of your hip. That point right there is the anterior-superior iliac spine. Due to its attachment, the sartorius flexes the leg at the knee and laterally rotates the thigh. This happens when we cross our legs.

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