Muscles Acting on the Foot

The fleshy mass of the leg proper (below the knee) is formed by a group of crural muscles, which act on the foot (fig. 10.35; table 10.19). These muscles are tightly bound together by deep fasciae, which compress them and aid in the return of blood from the legs. The fasciae separate the crural muscles into anterior, lateral, and posterior compartments, each with its own nerve and blood supply.

Muscles of the anterior compartment dorsiflex the ankle and prevent the toes from scuffing the ground during walking. These are the extensor digitorum longus (extensor of toes II-V), extensor hallucis53 longus (exten

53 halluc = great toe

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Table 10.18 Muscles Acting on the Knee (see figs. 10.32 and 10.34)

O = origin, I = insertion, N = innervation (n. = nerve)

Anterior (Extensor) Compartment of Thigh

Quadriceps Femoris (QUAD-rih-seps FEM-oh-riss)

Extends knee; rectus femoris also flexes hip

O: rectus femora—anterior inferior spine of ilium; I: tibial tuberosity vastus lateralis—posterolateral shaft of femur; vastus medialis—linea aspera of femur; vastus intermedius—anterior shaft of femur

N: femoral n.

Sartorius

Flexes hip and knee; rotates femur medially; rotates tibia laterally; used in crossing legs

O: anterior superior spine of ilium I: medial aspect of tibial tuberosity

N: femoral n.

Posterior (Flexor) Compartment of Thigh (Hamstring Group)

Biceps Femoris

Flexes knee; extends hip; laterally rotates leg

O: long ftead—ischial tuberosity; I: head of fibula short head—posterior midshaft of femur

N: long head—tibial n.; short head—common peroneal n.

Semimembranosus (SEM-ee-MEM-bran-OH-sis)

Flexes knee; extends hip; medially rotates tibia; tenses joint capsule of knee

O: ischial tuberosity I: medial condyle of tibia, collateral ligament of knee

N: tibial n.

Semitendinosus

Flexes knee; extends hip; medially rotates tibia

O: ischial tuberosity I: near tibial tuberosity

N: tibial n.

Posterior Compartment of Leg

Popliteus (pop-LIT-ee-us)

Unlocks knee to allow flexion; flexes knee; medially rotates tibia

O: lateral condyle of femur I: posterior proximal tibia

N: tibial n.

sor of the great toe), fibularis (peroneus54) tertius, and tibialis anterior. Their tendons are held tightly against the ankle and kept from bowing by two extensor retinacula similar to the one at the wrist (fig. 10.36).

The posterior compartment has superficial and deep muscle groups. The three muscles of the superficial group are plantar flexors—the gastrocnemius,55 soleus,56 and plantaris57 (fig. 10.37). The first two of these, collectively known as the triceps surae,58 insert on the calcaneus by

54peroneo = fibula

56named for its resemblance to a flatfish, the sole

57 planta = sole of foot

58sura = calf of leg way of the calcaneal (Achilles) tendon. This is the strongest tendon of the body but is nevertheless a common site of sports injuries resulting from sudden stress. The plantaris inserts medially on the calcaneus by a tendon of its own.

There are four muscles in the deep group (fig. 10.38). The flexor digitorum longus, flexor hallucis longus, and tibialis posterior are plantar flexors. The popliteus unlocks the knee joint so that it can be flexed and functions in flexion and medial rotation at the knee.

The lateral (peroneal) compartment includes the fibularis (peroneus) brevis and fibularis (peroneus) longus (figs. 10.37b, 10.38a, and 10.39b). They plantar flex and evert the foot. Plantar flexion is important not only in standing on tiptoes but in providing lift and forward thrust each time you take a step.

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Iliac crest

Iliopsoas

Iliacus Psoas major

Anterior superior ■ iliac spine

Tensor fasciae latae

Iliotibial band

Anterior superior ■ iliac spine

Tensor fasciae latae

Iliotibial band

Quadriceps Riss

Patellar ligament

Figure 10.32 Muscles of the Thigh. Anterior view. (a) Superficial muscles; (b) rectus femoris and other muscles removed to expose the other three heads of the quadriceps femoris.

Medial compartment Adductor magnus Pectineus Adductor brevis Adductor longus Gracilis

Anterior compartment

Sartorius

Quadriceps femoris Vastus intermedius Rectus femoris Vastus lateralis Vastus medialis

Quadriceps femoris tendon

Patella

Patellar ligament

Quadriceps femoris tendon

Patella

Quadricep Tear

Figure 10.32 Muscles of the Thigh. Anterior view. (a) Superficial muscles; (b) rectus femoris and other muscles removed to expose the other three heads of the quadriceps femoris.

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Femoral vein Femoral artery

Pectineus Adductor longus

Femoral vein Femoral artery

Superficial Layer Sartorius Horse

Tensor fasciae latae

Iliopsoas Sartorius

Iliotibial band

Quadriceps tendon Patella

Figure 10.33 Superficial Anterior Muscles of the Thigh of the Cadaver.

Tensor fasciae latae

Iliopsoas Sartorius

Iliotibial band

Quadriceps femoris Rectus femoris Vastus lateralis Vastus medialis

Quadriceps tendon Patella

Figure 10.33 Superficial Anterior Muscles of the Thigh of the Cadaver.

The intrinsic muscles of the foot support the arches and act on the toes in ways that aid locomotion (table 10.20). Several of them are similar in name and location to the intrinsic muscles of the hand. One of these muscles, the extensor digitorum brevis,59 is on the dorsal side of the foot. The others are ventral or lie between the metatarsals. They are grouped in four layers:

  1. The most superficial layer includes the stout flexor digitorum brevis medially, with four tendons that supply all the digits except the hallux. It is flanked by the abductor digiti minimi60 laterally and abductor hallucis61 medially; the tendons of these two muscles serve the little toe and great toe, respectively (fig. 10.40a).
  2. The second layer, deep to the first, consists of the thick medial quadratus plantae, which joins the tendons of the flexor digitorum longus, and the four

"short extensor of the digits"

60"abductor of the little toe"

61"abductor of the hallux (great toe)"

Great Toe Adductor

Figure 10.34 Gluteal and Thigh Muscles. Posterior view.

Gluteus medius Gluteus maximus Gracilis

Adductor magnus

Iliotibial band Vastus lateralis

Hamstring group Biceps femoris

Long head Short head

Semitendinosus

Semimembranosus

Figure 10.34 Gluteal and Thigh Muscles. Posterior view.

lumbrical muscles located between the metatarsals (fig. 10.40b).

  1. The third layer includes the adductor hallucis, flexor digiti minimi brevis, and flexor hallucis brevis (fig. 10.40c). The adductor hallucis has an oblique head that crosses the foot and inserts at the base of the great toe, and a transverse head that passes across the bases of digits II-V and meets the long head at the base of the hallux.
  2. The deepest layer consists of four dorsal interosseous muscles and three plantar interosseous muscles located between the metatarsals. Each dorsal interosseous muscle is bipennate and originates on two adjacent metatarsals. The plantar interosseous muscles are unipennate and originate on only one metatarsal each (fig. 10.40d, e).

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378 Part Two Support and Movement

Iliotibial band Biceps femoris

Fibularis longus Gastrocnemius Soleus

Fibularis brevis

Calcaneal tendon Lateral malleolus

Abductor digiti minimi

Iliotibial band Biceps femoris

Fibularis longus Gastrocnemius Soleus

Fibularis brevis

Calcaneal tendon Lateral malleolus

Abductor digiti minimi

Muscle Acting Foot

Patella

Patellar ligament

Tibialis anterior

Extensor digitorum longus

Extensor retinaculum

Extensor digitorum brevis

Tendons of extensor digitorum longus

Figure 10.35 Superficial Muscles of the Leg of the Cadaver. Right lateral view.

Patella

Patellar ligament

Tibialis anterior

Extensor digitorum longus

Extensor retinaculum

Extensor digitorum brevis

Tendons of extensor digitorum longus

Figure 10.35 Superficial Muscles of the Leg of the Cadaver. Right lateral view.

Table 10.19 Muscles Acting on the Foot (see figs.10.36 and 10.37)

O = origin, I = insertion, N = innervation (n. = nerve)

Anterior Compartment of Leg

Extensor Digitorum (DIDJ-ih-TOE-um) Longus

Extends toes II-V; dorsiflexes and everts foot

O: lateral condyle of tibia, shaft of fibula, interosseous membrane

I: middle and distal phalanges II-V

N: deep peroneal n.

Extensor Hallucis (hal-OO-sis) Longus

Extends hallux (great toe); dorsiflexes and inverts foot O: medial aspect of fibula, interosseous membrane

I: distal phalanx I

N: deep peroneal n.

Fibularis Tertius (FIB-you-LAIR-iss TUR-she-us)

Dorsiflexes and everts foot O: distal shaft of fibula

I: metatarsal V

N: deep peroneal n.

Tibialis (TIB-ee-AY-lis) Anterior

Dorsiflexes and inverts foot

O: lateral tibia, interosseous membrane

I: medial cuneiform, metatarsal I

N: deep peroneal n.

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Table 10.19 Muscles Acting on the Foot (see figs. 10.36 and 10.37) (continued)

Posterior Compartment of Leg—Superficial Group

Table 10.19 Muscles Acting on the Foot (see figs. 10.36 and 10.37) (continued)

Posterior Compartment of Leg—Superficial Group

Gastrocnemius (GAS-trock-NEE-me-us)

Flexes knee; plantar flexes foot O: medial and lateral epicondyles of femur

I: calcaneus

N: tibial n.

Soleus (SO-lee-us)

O: proximal one-third of tibia and fibula

I: calcaneus

N: tibial n.

Plantaris (plan-TERR-is)

Flexes knee; plantar flexes foot. Sometimes absent. O: distal femur

I: calcaneus

N: tibial n.

Posterior Compartment of Leg—Deep Group

Flexor Digitorum Longus

Flexes toes II-V; plantar flexes and inverts foot O: midshaft of tibia

I: distal phalanges II-V

N: tibial n.

Flexor Hallucis Longus

Flexes hallux (great toe); plantar flexes and inverts foot O: shaft of fibula

I: distal phalanx I

N: tibial n.

Tibialis Posterior

Plantar flexes and inverts foot

O: proximal half of tibia, fibula, interosseous membrane

I: navicular, cuneiforms, metatarsals II-IV Lateral (fibular) Compartment of Leg

N: tibial n.

Fibularis (peroneus) Brevis

Plantar flexes and everts foot O: shaft of fibula

I: base of metatarsal V

N: superficial peroneal n.

Fibularis (peroneus) Longus

Plantar flexes and everts foot

O: proximal half of fibula, lateral condyle of tibia

I: medial cuneiform, metatarsal I

N: superficial peroneal n.

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380 Part Two Support and Movement

Anterior And Medial Aspect The Thigh
Figure 10.36 Muscles of the Leg. Anterior view. (a) A view showing some muscles of the anterior, lateral, and posterior compartments. (b-d) Individual muscles of the anterior compartment of the leg and dorsal aspect of the foot.

Several of the muscles in the first three layers originate on a broad plantar aponeurosis, which lies between the plantar skin and muscles. It diverges like a fan from the calcaneus to the bases of all five toes.

_Think About It_

Not everyone has the same muscles. From the information provided in this chapter, identify two muscles that are lacking in some people.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

  1. In the middle of a stride, you have one foot on the ground and you are about to swing the other leg forward. What muscles produce the movements of that leg?
  2. Name the muscles that cross both the hip and knee joints and produce actions at both.
  3. List the major actions of the muscles of the anterior, medial, and posterior compartments of the thigh.
  4. Describe the role of plantar flexion and dorsiflexion in walking. What muscles produce these actions?

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Posterior Crural Muscles
Figure 10.37 Superficial Muscles of the Leg, Posterior Compartment. (a) The gastrocnemius. (b) The soleus, deep to the gastrocnemius and sharing the calcaneal tendon with it.

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382 Part Two Support and Movement

Soleus Muscle Tear
Figure 10.38 Deep Muscles of the Leg, Posterior and Lateral Compartments. (a) Muscles deep to the soleus. (b-d) Exposure of some individual deep muscles with foot plantar flexed.

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Biceps femoris Long head Short head

Femur -

Vastus lateralis Vastus intermedius Rectus femoris

Adductors Bowing Femur

Sartorius Vastus medialis

Semitendinosus Semimembranosus Adductor magnus Gracilis

Adductor brevis Adductor longus

Sartorius Vastus medialis

Gastrocnemius (lateral head)

Lateral Head Gastrocnemius

Gastrocnemius (medial head)

Soleus

Flexor hallucis longus Flexor digitorum longus Tibialis posterior

Tibia

Tibialis anterior

Gastrocnemius (lateral head)

Fibula

Fibularis longus Fibularis brevis Extensor hallucis longus Extensor digitorum longus

Gastrocnemius (medial head)

Soleus

Flexor hallucis longus Flexor digitorum longus Tibialis posterior

Tibia

Tibialis anterior

Key a

  • Posterior compartment (hamstrings)
  • Medial compartment B Anterior compartment

Key b

| Posterior superficial compartment

Posterior deep compartment | Lateral (fibular) compartment Anterior compartment

Figure 10.39 Serial Cross Sections Through the Lower Limb. Each section is taken at the correspondingly lettered level at the bottom of the figure and is pictured with the posterior muscle compartment facing the top of the page. Which of these muscles are named for the adjacent bones?

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Table 10.20 Intrinsic Muscles of the Foot (see fig. 10.40)

O = origin, I = insertion, N = innervation (n. = nerve, nn. = nerves)

Dorsal Aspect of Foot

Extensor Digitorum (DIDJ-ih-TOE-rum) Brevis

Extends toes

O: dorsal aspect of calcaneus I: tendons of extensor digitorum longus

N: deep peroneal n.

Ventral Layer 1 (Most Superficial)

Flexor Digitorum Brevis

Flexes toes II-V

O: calcaneus, plantar aponeurosis I: middle phalanges II-V

N: medial plantar n.

Abductor Digiti Minimi

Abducts and flexes little toe; supports lateral longitudinal arch

O: calcaneus, plantar aponeurosis I: proximal phalanx V

N: lateral plantar n.

Abductor Hallucis (hal-OO-sis)

Flexes hallux (great toe); supports medial longitudinal arch

O: calcaneus, plantar aponeurosis I: proximal phalanx I

N: medial plantar n.

Ventral Layer 2

Quadratus Plantae (quad-RAY-tus PLAN-tee)

Flexes toes

O: calcaneus, plantar aponeurosis I: tendons of flexor digitorum

N: lateral plantar n.

Lumbricals (four muscles)

Flex metatarsophalangeal joints; extend interphalangeal joints

O: tendon of flexor digitorum longus I: extensor tendons to digits II-V

N: lateral and medial plantar nn.

Ventral Layer 3

Adductor Hallucis

Adducts hallux

O: metatarsals II-IV I: proximal phalanx I

N: medial plantar n.

Flexor Digiti Minimi Brevis

O: metatarsal V, plantar aponeurosis I: proximal phalanx V

N: lateral plantar n.

Flexor Hallucis Brevis

O: cuboid, plantar aponeurosis I: proximal phalanx I

N: medial plantar n.

Ventral Layer 4 (Deepest)

Dorsal Interosseous Muscles (four muscles)

Abduct toes II-V

O: each with two heads arising from adjacent metatarsals I: proximal phalanges II-IV

N: lateral plantar n.

Plantar Interosseous Muscles (three muscles)

O: medial aspect of metatarsals III-V I: proximal phalanges III-V

N: lateral plantar n.

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Chapter 10 The Muscular System 385

Flexor digiti minimi brevis

Abductor digiti minimi

Flexor digiti minimi brevis

Abductor digiti minimi

Abductor Digiti Minimi Calcaneus

Abductor hallucis

Flexor digitorum brevis

Plantar fascia (cut)

Calcaneus

Abductor hallucis

Flexor digitorum brevis

Plantar fascia (cut)

Calcaneus

Quadratus plantae

Flexor digitorum-brevis (cut)

Quadratus plantae

Flexor digitorum-brevis (cut)

Plantar Fascia Extensor Hallucis Tendon

Lumbricals

Flexor hallucis longus tendon

Flexor digitorum longus tendon Abductor hallucis (cut)

Flexor digiti minimi brevis

Quadratus plantae (cut)

Flexor digiti minimi brevis

Quadratus plantae (cut)

Adductor Hallucis Release

Plantar view

-Adductor hallucis

Plantar

Flexor hallucis brevis interosseous

-Flexor hallucis longus tendon (cut)

Abductor hallucis (cut)

Flexor digitorum longus tendon (cut)

Plantar

Flexor hallucis brevis interosseous

Lumbricals The Foot Diseases

Dorsal interosseous

Dorsal view

Dorsal interosseous

Atrophy First Dorsal Interosseous

Figure 10.40 Intrinsic Muscles of the Foot. (a-d) First through fourth layers, respectively, in ventral (plantar) views; (e) fourth layer, dorsal view.

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386 Part Two Support and Movement

Insight 10.6 Clinical Application

Athletic Injuries

Although the muscular system is subject to fewer diseases than most organ systems, it is particularly vulnerable to injuries resulting from sudden and intense stress placed on muscles and tendons. Each year, thousands of athletes from the high school to professional level sustain some type of injury to their muscles, as do the increasing numbers of people who have taken up running and other forms of physical conditioning. Overzealous exertion without proper conditioning and warm-up is frequently the cause. Some of the more common athletic injuries are:

Baseball finger—tears in the extensor tendons of the fingers resulting from the impact of a baseball with the extended fingertip.

Blocker's arm—ectopic ossification in the lateral margin of the forearm as a result of repeated impact with opposing players.

Charley horse—any painful tear, stiffness, and blood clotting in a muscle. A charley horse of the quadriceps femoris is often caused by football tackles.

Compartment syndrome—a condition in which overuse, contusion, or muscle strain damages blood vessels in a compartment of the arm or leg. Since the fasciae enclosing a compartment are tight and cannot stretch, blood or tissue fluid accumulating in the compartment can put pressure on the muscles, nerves, and blood vessels. The lack of blood flow in the compartment can cause destruction of nerves if untreated within 2 to 4 hours and death of muscle tissue if it goes untreated for 6 hours or more. Nerves can regenerate if blood flow is restored, but muscle damage is irreversible. Depending on its severity, compartment syndrome may be treated with immobilization and rest or an incision to drain fluid from the compartment or otherwise relieve the pressure.

Pitcher's arm—inflammation at the origin of the flexor carpi resulting from hard wrist flexion in releasing a baseball.

Pulled groin—strain in the adductor muscles of the thigh. It is common in gymnasts and dancers who perform splits and high kicks.

Pulled hamstrings—strained hamstring muscles or a partial tear in the tendinous origin, often with a hematoma (blood clot) in the fascia lata. This condition is frequently caused by repetitive kicking (as in football and soccer) or long, hard running.

Rider's bones—abnormal ossification in the tendons of the adductor muscles of the medial thigh. It results from prolonged abduction of the thighs when riding horses.

Rotator cuff injury—a tear in the tendon of any of the SITS (rotator cuff) muscles, most often the tendon of the supraspinatus. Such injuries are caused by strenuous circumduction of the arm, shoulder dislocation, or repetitive use of the arm in a position above horizontal. They are common among baseball pitchers and third basemen, bowlers, swimmers, weight lifters, and in racquet sports. Recurrent inflammation of a SITS tendon can cause a tendon to degenerate and then to rupture in response to moderate stress. Injury causes pain and makes the shoulder joint unstable and subject to dislocation.

Shinsplints—a general term embracing several kinds of injury with pain in the crural region: tendinitis of the tibialis posterior muscle, inflammation of the tibial periosteum, and anterior compartment syndrome. Shinsplints may result from unaccustomed jogging, walking on snowshoes, or any vigorous activity of the legs after a period of relative inactivity.

Tennis elbow—inflammation at the origin of the extensor carpi muscles on the lateral epicondyle of the humerus. It occurs when these muscles are repeatedly tensed during backhand strokes and then strained by sudden impact with the tennis ball. Any activity that requires rotary movements of the forearm and a firm grip of the hand (for example, using a screwdriver) can cause the symptoms of tennis elbow.

Tennis leg—a partial tear in the lateral origin of the gastrocnemius muscle. It results from repeated strains put on the muscle while supporting the body weight on the toes.

Most athletic injuries can be prevented by proper conditioning. A person who suddenly takes up vigorous exercise may not have sufficient muscle and bone mass to withstand the stresses such exercise entails. These must be developed gradually. Stretching exercises keep ligaments and joint capsules supple and therefore reduce injuries. Warm-up exercises promote more efficient and less injurious musculoskeletal function in several ways, discussed in chapter 11. Most of all, moderation is important, as most injuries simply result from overuse of the muscles. "No pain, no gain" is a dangerous misconception.

Muscular injuries can be treated initially with "RICE": rest, ice, compression, and elevation. Rest prevents further injury and allows repair processes to occur; ice reduces swelling; compression with an elastic bandage helps to prevent fluid accumulation and swelling; and elevation of an injured limb promotes drainage of blood from the affected area and limits further swelling. If these measures are not enough, anti-inflammatory drugs may be employed, including corticosteroids as well as aspirin and other nonsteroidal agents.

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Chapter 1G The Muscular System 387

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Responses

  • kia
    What muscle is straining anterolateral leg?
    6 years ago
  • leon
    What muscle is anterior to gastrocnemius?
    3 years ago
  • MEBRAHTU SIMON
    Where is anterolateral side of mid thigh wid pics.?
    3 years ago
  • marko
    Which muscle is deep to the gastrocnemius?
    1 year ago

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