Muscles in the Leg
By Joe Stubits, PTA
Muscles in the Leg
The muscle of the legs, support, balance and propel the body. These muscles can exert a lot of power while continuously making slight adjustments for balance whether the body is moving or at rest. From the big, strong muscles of the buttocks and legs to the little, fine muscles of the feet and toes, the muscle of the legs play an important role in our everyday activities.
The majority of the muscles in the leg cover a large distance and are considered to belong to muscles. When these muscles contract and relax, they move skeletal bones to generate movement of the body. Smaller muscles assist the larger muscles to stabilize joints, aid with rotation of joints, and help with other fine-tuned movements.
The biggest muscle masses in the leg are found in the thigh and the calf.
The quadriceps consists of four muscles. These four muscles are the strongest and leanest of all muscles in the human body. Located at the front of the thigh, the quadriceps are the major extensors (help to extend the leg straight) 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, or patella.
- 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 muscles.
- Rectus femoris: This muscle attaches to the kneecap. Of the quadriceps muscles, it has the least affect on extension of the knee. This muscle also helps produce flexion at the hip joint.
The hamstrings consist of 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 bends 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, bends the knee, and helps rotate the tibia.
- Semitendinosus: This muscle also extends the thigh and bends the knee.
The calf muscles are crucial 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 bends the knee and performs plantar flexion at the ankle (pointing toes away).
- Soleus: This muscle extends from the back of the knee to the heel. It is essential in walking and standing.
- Plantaris: This small, slender muscle is absent in about 10 percent of people. The plantaris is a weak plantar flexor at the ankle and flexor at the knee.
Perhaps the most significant tendon in terms of mobility is the Achilles tendon. This vital 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 required for running, jumping, and other physical activity.
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Written by: Joe Stubits, PTA