Anatomy of the thigh

The thigh is divided into a front, back, outer, and inner side. In each region lie muscles with a different function. In addition to the muscles, blood vessels and nerves also run here that supply and control the muscles.
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The bones of the thigh

In the thigh lies the thighbone, the femur. This is a long bone with a large rounded head at the top that, together with the socket of the pelvis, forms the hip joint.

At the bottom, the thighbone consists of two half-round articular surfaces that rest on the shinbone and together form the knee joint.

Then there is the kneecap, the patella. This is woven into the tendon of the knee extensors. During bending and extending of the knee, the kneecap glides in a kind of groove of the thighbone. This is the patellofemoral joint.

The knee extensors

The front of the thigh is largely covered by the muscles that extend the knee. This group of muscles is called the musculus quadriceps femoris, which means four-headed thigh muscle. This name is not entirely correct. A few years ago, a fifth muscle was discovered. It lies well hidden between the other parts. As such, the quadriceps consists of the following five muscles:

• Rectus femoris
• Vastus intermedius
• Tensor vastus intermedius
• Vastus lateralis
• Vastus medialis

Although these muscles all start in a different place, the end for most is the same. They attach to the kneecap, which acts like a lever and makes extension easier. Below the kneecap, the patellar tendon continues to the shinbone. This makes the quadriceps a powerful knee extensor.

The rectus femoris is the only quadriceps muscle that attaches to the pelvis. Therefore, this muscle also assists with flexing the hip joint. The other muscles start on the thigh.

The tailor's muscle

Diagonally across the thigh runs the longest muscle in our body, the tailor's muscle (sartorius). This slender muscle begins on the outside of the pelvis and then runs diagonally down toward the inside of the knee. Because it is maximally tensed in the tailor's sitting position, it is called the tailor's muscle. Slightly toward the middle of this muscle lies the femoral artery. In many people you can feel the pulse here.

The tailor's muscle ends just below the knee joint. At the same point, two other tendons come together. These are the tendons of the semitendinosus and the gracilis. This spot therefore resembles a kind of goose foot, the pes anserinus.

The knee flexors

At the back of the thigh lie the knee flexors (hamstrings). They mainly provide flexion of the knee and rotation of the lower leg.
This muscle group consists of three muscles:

• Biceps femoris
• Semimembranosus
• Semitendinosus

The biceps femoris itself consists of two muscle bellies: a long head that attaches to the sit bone and a short head that begins on the thighbone. They end with a common tendon on the fibula.

The large leg nerve

Over the back of the thigh runs the large leg nerve (nervus ischiadicus). This is a thick and long nerve that comes from the lower back and controls the muscles of the leg and foot.

The muscles on the inside of the thigh

On the inside of the thigh are the adductors. They mainly move the thigh inward and are active, among other things, during kicking movements. These muscles begin in the groin and fan out to the thighbone and the shinbone. There are shorter and longer groin muscles. These are the following muscles:

• Pectineus
• Adductor longus
• Adductor brevis
• Adductor magnus
• Gracilis

The tendon sheet on the outside of the thigh

On the outside of the thigh, at the level of the hip, there is a short muscle with a very long and wide tendon sheet that covers the entire side of the thigh (tensor fascia latae). It is one of the muscles that lifts the leg sideways when it contracts.