The thigh bears much of the load of the body’s weight when a person is upright. It contains many muscles and nerves but only has one bone, the femur, which is the longest and strongest bone in the human body.
The four muscles that make up the quadriceps are the strongest and leanest of all muscles in the body. These muscles at the front of the thigh are the major extensors (help to extend the leg straight) of the knee. They are:
- Vastus lateralis
- Vastus medialis
- Vastus intermedius
- Rectus femoris
These four muscles come together to form a single tendon, which inserts into the patella, or kneecap.
Other muscles of the anterior (front) thigh include the pectineus, sartorius, and theiliopsoas, which is made up of the psoas major and iliacus.
Muscles in the medial thigh help to bring the thigh toward the midline of the body and rotate it. These muscles are the adductor longus, adductor brevis, adductor magnus, gracilis, and the obturator externus.
The hamstrings are three muscles at the back of the thigh that affect hip and knee movement. They begin under the gluteus maximus behind the hipbone and attach to the tibia at the knee. They are:
- Biceps femoris
Nerve supply to the thigh comes from various lumbar and sacral nerves via the femoral, obturator, and common peroneal nerves. The tibial and sciatic nerves also supply parts of the thigh.
The only bone in the thigh is the femur, which extends from the hip to the knee. It can resist forces of 1,800 to 2,500 pounds, so it is not easily fractured.
Branches of the femoral artery supply the thigh with oxygen-rich blood. The femoral artery is divided into a superficial, deep, and common arteries, and these further divide into branches, including the medial and lateral circumflex arteries. The largest branch of the femoral artery is the deep femoral artery, also called the profunda femoris. The femoral vein runs alongside the femoral artery and also has many branches. It takes oxygen-depleted blood from the thigh on a path back toward the heart.
Common problems with the thigh are often the result of participation in sports or repetitive movements. These include:
- Muscle strains (pulls or tears)
- Muscle cramps
- Contusions (bruises)
- Tendonitis (inflammation of a tendon)
- Sciatica (pain from the sciatic nerve)