Muscles of the Legs

A Visual Guide

Muscles of the Legs

7. Deep Muscles

6. Superficial Compartment

5. Calf Muscles

4. Texto/Imagen 2

3. Posterior Thigh Muscles

2. Anterior Thigh Muscles

1. Why Study Leg Muscles?

ÍNDICE

Why Study Leg Muscles?

Quadriceps

iliopsoas

The muscles of the anterior compartment of the thigh are a group of muscles that (mostly) act to extend the lower limb at the knee joint.

Anterior Thigh Muscles

The muscles located within the posterior compartment of the thigh are the biceps femoris, semitendinosus and semimembranosus.

Posterior Thigh Muscles

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The posterior compartment of the leg contains seven muscles and can be subdivided into superficial and deep compartments. The muscles in this compartment act to plantarflex and invert the foot. They are innervated by the tibial nerve (a branch of the sciatic nerve). Blood supply chiefly from the posterior tibial artery.

Calf Muscles

There are three muscles within the superficial compartment of the posterior leg. They all insert onto the calcaneus (heel bone) of the foot, via the calcaneal tendon. To minimise friction during movement, there are two bursae (fluid filled sacs) associated with the calcaneal tendon:

• Subcutaneous calcaneal bursa – lies between the skin and the calcaneal tendon.
• Deep bursa of the calcaneal tendon – lies between the tendon and the calcaneus.

Superficial Compartment

There are four muscles in the deep compartment of the posterior leg. One muscle, the popliteus, acts only on the knee joint. The remaining three muscles (tibialis posterior, flexor hallucis longus and flexor digitorum longus) act on the ankle and foot.

Deep Muscles

There are four muscles in the deep compartment of the posterior leg. One muscle, the popliteus, acts only on the knee joint. The remaining three muscles (tibialis posterior, flexor hallucis longus and flexor digitorum longus) act on the ankle and foot.

Deep Muscles

The iliopsoas is comprised of two separate muscles; the psoas major and iliacus. These muscles arise in the pelvis and pass under the inguinal ligament into the anterior compartment of the thigh – where they form a common tendon. Unlike many of the anterior thigh muscles, the iliopsoas does not perform extension of the leg at the knee joint.

Attachments: The psoas major originates from the lumbar vertebrae, and the iliacus originates from the iliac fossa of the pelvis. They insert together onto the lesser trochanter of the femur. Actions: Flexion of the the thigh at the hip joint. Innervation: The psoas major is innervated by anterior rami of L1-3, while the iliacus is innervated by the femoral nerve.

The quadriceps femoris consists of four individual muscles – the three vastus muscles and the rectus femoris. It forms the main bulk of the anterior thigh, and is one of the most powerful muscles in the body. The four muscles collectively insert onto the patella via the quadriceps tendon. The patella, in turn, is attached to the tibial tuberosity by the patella ligament.

Attachments: Originates from the anterior superior iliac spine, and attaches to the superior, medial surface of the tibia. Actions: At the hip joint, it is a flexor, abductor and lateral rotator. At the knee joint, it is also a flexor. Innervation: Femoral nerve.

Attachments: Originates from the anterior inferior iliac spine and the ilium of the pelvis. It attaches to the patella via the quadriceps femoris tendon. Actions: Extension of the knee joint and flexion of the hip joint (it is the only muscle of the quadriceps group to cross both the hip and knee joints).Innervation: Femoral nerve.

Attachments: Originates from the pectineal line of the pubis bone. It inserts onto the pectineal line on the posterior aspect of the femur, immediately inferior to the lesser trochanter. Actions: Adduction and flexion at the hip joint. Innervation: Femoral nerve. May also receive a branch from the obturator nerve.

Attachments: The long head originates from the ischial tuberosity of the pelvis.Actions: Main action is flexion at the knee. It also extends the thigh at the hip, and laterally rotates at the hip and knee. Innervation: The short head is innervated by the common fibular part of the sciatic nerve.

Attachments: The short head originates from the linea aspera on posterior surface of the femur. Together, the heads form a tendon, which inserts into the head of the fibula. Actions: Main action is flexion at the knee. It also extends the thigh at the hip, and laterally rotates at the hip and knee. Innervation: The short head is innervated by the common fibular part of the sciatic nerve.

Attachments: Originates from the ischial tuberosity of the pelvis and attaches to the medial surface of the tibia. Actions: Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint.Innervation: Tibial part of the sciatic nerve.

Attachments: Originates from the ischial tuberosity (more superiorly than the origin of the semitendinosus and biceps femoris). Attaches to the medial tibial condyle.Actions: Flexion of the leg at the knee joint. Extension of thigh at the hip. Medially rotates the thigh at the hip joint and the leg at the knee joint. Innervation: Tibial part of the sciatic nerve.

• Attachments:

The lateral head originates from the lateral femoral condyle. The medial head originates from the medial femoral condyle.The two heads combine to form a single muscle belly.Distally, the muscle belly converges with the soleus muscle to form the calcaneal tendon. This inserts onto the calcaneus.

• Actions: Plantarflexion at the ankle joint and flexion at the knee joint.

• Innervation: Tibial nerve.

• Attachments: Originates from the soleal line of the tibia and proximal fibula. The muscle converges with the fibres of the gastrocnemius to form the calcaneal tendon, which inserts onto the calcaneus.

• Actions: Plantarflexion of the foot at the ankle joint.

• Innervation: Tibial nerve

• Attachments: Originates from the lateral supracondylar line of the femur. The fibres condense into a tendon which travels down the leg, between the gastrocnemius and soleus muscles. It blends with the calcaneal tendon and inserts onto the calcaneus.

• Actions: Contributes to plantarflexion at the ankle joint and flexion at the knee joint.

• Innervation: Tibial nerve.

Attachments: Originates from the lateral condyle of the femur and the lateral meniscus of the knee joint. It inserts onto the proximal tibia, immediately above the origin of the soleus muscle. Actions: Lateral rotation of the femur relative to the tibia. This ‘unlocks’ the knee joint so that flexion can occur. Innervation: Tibial nerve

Attachments: Originates from the medial surface of the tibia and attaches to the plantar surfaces of the lateral four digits.Actions: Flexion of the lateral four toes. Innervation: Tibial nerve

Attachments: Originates from the posterior surface of the fibula and attaches to the plantar surface of the phalanx of the great toe.Actions: Flexion of the great toe. Innervation: Tibial nerve

Attachments: Originates from the posterior surface and interosseous membrane of the tibia and fibula. The tendon enters the foot posterior to the medial malleolus and attaches to the plantar surfaces of the medial tarsal bones. Actions: Inversion and plantarflexion of the foot. It also contributes to the medial arch of the foot. Innervation: Tibial nerve