Anatomy of the thigh

The thigh is divided into four regions: front, back, outer, and inner. Each region contains muscles with distinct functions. Additionally, blood vessels and nerves traverse the thigh, supplying and controlling the muscles.
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The bones of the thigh

In the thigh lies the thigh bone, 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 lower end the femur consists of two semicircular joint surfaces that rest on the shin bone and together form the knee joint.

Then there is the kneecap, the patella. This is embedded in the tendon of the knee extensors. During bending and straightening of the knee, the kneecap glides in a kind of groove of the femur. 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. This lies well hidden between the other parts. Thus, the quadriceps consists of the following five muscles:

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

Although these muscles all originate in different places, most of them end in the same way. They attach to the kneecap, which acts as a kind of lever and makes extension easier. Below the kneecap, the patellar tendon continues to the shin bone. This makes the quadriceps a powerful knee extensor.

The rectus femoris is the only quadriceps muscle that attaches to the pelvis. As a result, this muscle also helps to flex the hip joint. The other muscles start on the thigh.

The sartorius muscle

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

The sartorius ends just below the knee joint. At the same point, two other tendons come together: those of the semitendinosus and the gracilis. This place therefore resembles a kind of goose's foot, the pes anserinus.

The knee flexors

At the back of the thigh lie the knee flexors (hamstrings). They are mainly responsible for bending the knee and rotating 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 ischial tuberosity and a short head that begins on the femur. They end with a common tendon on the fibula.

The large leg nerve

Running down the back of the thigh is the large leg nerve (nervus ischiadicus, or sciatic nerve). This is a thick and long nerve that originates in the lower back and controls the muscles of the leg and foot.

The muscles on the inner side of the thigh

On the inner side of the thigh are the adductors. They mainly move the thigh inwards and are active, among other things, during kicking movements. These muscles begin in the groin and fan out to the thigh bone and shin bone. There are shorter and longer groin muscles. These are the following muscles:

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

The iliotibial tract on the outer side of the thigh

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