The majority of muscles in the leg are considered long
muscles, in that they stretch great distances. As these muscles contract and
relax, they move skeletal bones to create movement of the body. Smaller muscles
help the larger muscles, stabilize joints, help rotate joints, and facilitate other
fine-tuned movements.
The largest muscle masses in the leg are present in the
thigh and the calf.
The quadriceps
are the strongest and leanest muscles in the body. These four muscles at the
front of the thigh are the major extensors of the knee. They are:
- Vastus
lateralis: On the outside of the thigh, this is the largest of the
quadriceps. It extends from the top of the femur to the kneecap.
- Vastus
medialis: This teardrop-shaped muscle of the inner thigh attaches along the
femur and down to the inner border of the kneecap.
- Vastus
intermedius: Between the vastus medialis and the vastus lateralis at the
front of the femur, it is the deepest of the quadriceps.
- Rectus
femoris: This muscle attaches to the kneecap. Of the four quadriceps
muscles, it has the least affect on flexing the knee.
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: This long muscle flexes the knee. It begins in the thigh area and
extends to the head of the fibula near the knee.
- Semimembranosus:
This long muscle extends from the pelvis to the tibia. It extends the thigh,
flexes the knee, and helps rotate the tibia.
- Semitendinosus:
This muscle also extends the thigh and flexes the knee.
The calf muscles are pivotal to movement of the ankle, foot,
and toes. Some of the major muscles of the calf include:
- Gastrocnemius
(calf muscle): One of the large muscles of the leg, it connects to the heel.
It flexes and extends the foot, ankle, and knee.
- Soleus:
This muscle extends from the back of the knee to the heel. It is important in
walking and standing.
- Plantaris:
This small, thin muscle is absent in about 10 percent of people. The
gastrocnemius muscle supersedes its function.
Possibly the most important
tendon in terms of mobility is the Achilles
tendon. This important tendon in the back of the calf and ankle connects
the plantaris, gastrocnemius, and soleus muscles to the heel bone. It stores
the elastic energy needed for running, jumping, and other physical activity.
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