11. Muscles of the Leg and Foot



Muscles of the Leg and Foot


The muscles of this chapter are primarily involved with motions of the foot at the ankle and subtalar joints and/or the motions of the toes at the metatarsophalangeal (MTP) and interphalangeal (IP) joints.


As a rule, muscles that move the foot originate (attach proximally) and have their bellies in the leg. Leg muscles are usually divided into the four fascial compartments of the leg: anterior, lateral, superficial posterior, and deep posterior.


The anterior compartment contains the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius.


The lateral compartment contains the fibularis longus and fibularis brevis.


The superficial posterior compartment contains the gastrocnemius, soleus, and plantaris.


The deep posterior compartment contains the tibialis posterior, flexor digitorum longus, flexor hallucis longus, and popliteus. Some of these muscles are addressed in other chapters.


The location by compartment helps determine the actions of these muscles. For example, all muscles of the anterior compartment perform dorsiflexion; all muscles of the lateral and posterior compartments perform plantarflexion; and all muscles of the lateral compartment perform eversion. The final determination of exactly what the actions of a muscle of the ankle and subtalar joints will be is where the distal tendon of that muscle crosses these joints (e.g., the belly of the tibialis anterior is located in the anterolateral leg, but its tendon crosses the subtalar joint medially; therefore it inverts the foot).


Muscles that move the toes are usually divided into long extrinsic foot muscles and short intrinsic foot muscles. Extrinsic foot muscles originate (attach proximally) in the leg or thigh and insert (attach distally) in the foot. Intrinsic foot muscles originate and insert (attach proximally and distally) in the foot; in other words, they are wholly located in the foot. The intrinsics of the foot are divided into dorsal and plantar muscles. Generally, dorsal muscles extend the toes; plantar muscles flex the toes. The plantar muscles are further divided into four layers, named Layers I through IV, from superficial to deep. The term digitorum refers to toes two through five; the term hallucis refers to the big toe.


The companion CD at the back of this book allows you to examine the muscles of this body region, layer by layer, and individual muscle palpation technique videos are available in the Chapter 11 folder on the Evolve website.


OVERVIEW OF FUNCTION: MUSCLES OF THE ANKLE AND SUBTALAR JOINTS


The following general rules regarding actions can be stated for the functional groups of muscles of the ankle and subtalar joints:



ent If a muscle crosses the ankle joint anteriorly with a vertical direction to its fibers, it can dorsiflex the foot at the ankle joint by moving the dorsum of the foot toward the anterior (dorsal) surface of the leg.


ent If a muscle crosses the ankle joint posteriorly with a vertical direction to its fibers, it can plantarflex the foot at the ankle joint by moving the plantar surface of the foot toward the posterior surface of the leg.


ent If a muscle crosses the subtalar joint laterally, it can evert the foot at the subtalar joint by moving the lateral surface of the foot toward the lateral surface of the leg. Note: Eversion is the principle component of pronation.


ent If a muscle crosses the subtalar joint medially, it can invert the foot at the subtalar joint by moving the medial surface of the foot toward the medial surface of the leg. Note: Inversion is the principle component of supination.


ent Reverse actions occur when the foot is planted on the ground and the leg must move relative to the foot. The same terms can be used to describe these reverse actions. For example, when the anterior (dorsal) surface of the leg moves toward the dorsum of the foot, it is called dorsiflexion of the leg at the ankle joint.


OVERVIEW OF FUNCTION: MUSCLES OF THE TOES


The following general rules regarding actions can be stated for the functional groups of toe muscles:



ent Toes two through five can move at three joints: the MTP, proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints. The big toe (toe one) can move at two joints: the MTP and IP joints.


ent To move a joint of the toe, the muscle must cross that joint; therefore knowing the attachments of the toe muscles determines which toe joints can be moved by that muscle.


ent If a muscle crosses the joints of the toes on the plantar side, it can flex the toe at the joint(s) crossed; if a muscle crosses joints of the toes on the dorsal side, it can extend the toe at the joint(s) crossed.


ent Reverse actions involve the origin (proximal attachment) moving toward the insertion (distal one). This occurs when the distal end of the foot is fixed, usually when the foot is planted on the ground (for example, when we toe-off during the gait cycle, the metatarsals of the toes extend toward the proximal phalanger, and therefore the foot extends toward the toes at the MTP joints).



MUSCLES OF THE LEG AND FOOT



ATTACHMENTS


Origin (Proximal Attachment)



Insertion (Distal Attachment)



ACTIONS



STABILIZATION

Stabilizes the ankle and subtalar joints.


INNERVATION



PALPATION





ATTACHMENTS


Origin (Proximal Attachment)



Insertion (Distal Attachment)



ACTIONS


The extensor hallucis longus moves the foot at the ankle and subtalar joints and the big toe at the metatarsophalangeal (MTP) and interphalangeal (IP) joints.



STABILIZATION

Stabilizes the ankle and subtalar joints and the MTP and IP joints of the big toe.


INNERVATION



PALPATION




TREATMENT CONSIDERATION


When we swing forward during the gait cycle, we usually extend our toes so they do not drag on the ground.


image


ATTACHMENTS


Origin (Proximal Attachment)



Insertion (Distal Attachment)



ACTIONS


The extensor digitorum longus moves the foot at the ankle and subtalar joints and toes two through five at the metatarsophalangeal (MTP) and interphalangeal (IP–proximal interphalangeal [PIP] and distal interphalangeal [DIP] joints).



STABILIZATION

Stabilizes the ankle and subtalar joints, and the MTP and IP joints of toes two through five.


INNERVATION



PALPATION




TREATMENT CONSIDERATIONS



MUSCLES OF THE LEG AND FOOT: Fibularis Group




ACTIONS


Fibularis Longus and Fibularis Brevis



Fibularis Tertius



STABILIZATION

Stabilize the ankle and subtalar joints.


INNERVATION



PALPATION


Fibularis Longus and Fibularis Brevis



1. The client is side lying. Place your palpating finger pads on the lateral side of the fibula, just distal to the head of the fibula. Place the resistance hand on the lateral side of the foot.


2. Resist the client from everting the foot at the subtalar joint. Feel for the contraction of the fibularis longus (Figure 11-14, A).


3. Continue palpating the fibularis longus distally by strumming perpendicular to the fibers. The fibularis longus becomes tendon approximately halfway down the leg. The distal tendon can usually be seen immediately posterior to the lateral malleolus of the fibula (Figure 11-14, B).


4. To palpate the fibularis brevis, palpate on either side of the fibularis longus in the distal half of the leg (Figure 11-15, A).


5. The distal tendon of the fibularis brevis is often visible and palpable in the proximal foot distal to the lateral malleolus of the fibula (Figure 11-15, B).





TREATMENT CONSIDERATIONS



ent The distal tendon of the fibularis longus follows an unusual path; it crosses posterior to the lateral malleolus to enter the lateral side of the foot, where it crosses posterior to the cuboid and then dives deep into the plantar side of the foot. It finally attaches onto the medial side of the foot at the same location as the attachment of the tibialis anterior (first cuneiform and first metatarsal).


ent The fibularis longus and the tibialis anterior are known as the stirrup muscles. These two muscles both attach at the same location on the medial foot and may be viewed to act as a stirrup to support the arch structure of the foot.


image

ent The fibularis longus and the fibularis brevis should be strengthened in people who have had inversion sprains of the ankle joint.


ent The fibularis tertius is actually the most distal and lateral part of the extensor digitorum longus. Its fibers do not attach onto a digit (a phalanx); for this reason the fibularis tertius is given a separate name and considered to be a separate muscle from the extensor digitorum longus.


image

ent The fibularis tertius is sometimes missing.


Notes



Aug 22, 2016 | Posted by in MUSCULOSKELETAL MEDICINE | Comments Off on 11. Muscles of the Leg and Foot
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