In human anatomy, the lower leg or
crus (or shank) is the part of the lower limb that lies between the
knee and the
ankle. In the lower leg, the
calf is the back portion, and the
tibia or shinbone together with the smaller
fibula make up the
shin, the front of the lower leg. Anatomists restrict the term
leg to this use, rather than to the entire lower limb. The
thigh is between the
hip and
knee and makes up the rest of the lower limb. While the capacity to walk upright is not unique to humans, other
primates can only achieve this for short periods and at a great expenditure of energy. The human adaption to bipedalism has also affected the location of the body's
center of gravity, the reorganization of
internal organs, and the form and
biomechanism of the trunk. In humans, the double S-shaped
vertebral column acts as a great shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are exceptionally long and powerful as a result of their exclusive specialization for support and locomotion—in
orangutans the leg length is 111% of the trunk; in
chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to
bipedalism, most substantially the
gluteal muscles, the extensors of the
knee joint, and the
calf muscles.
Bones The major
bones of the leg are the
femur (thigh bone),
tibia (shin bone), and adjacent
fibula, which are all
long bones. The
patella (kneecap) is a
sesamoid bone (the largest in the body) in front of the
knee. Most of the leg skeleton has bony prominences and margins that can be
palpated, and some serve as
anatomical landmarks that define the extent of the leg. These landmarks are the
anterior superior iliac spine, the
greater trochanter, the superior margin of the
medial condyle of tibia, and the
medial malleolus. Notable exceptions to palpation are the
hip joint, and the
neck and
body, or shaft of the femur. Usually, the large
joints of the lower limb are aligned in a straight line, which represents the mechanical longitudinal axis of the leg, the
Mikulicz line. This line stretches from the
hip joint (or more precisely the
head of the femur), through the
knee joint (the
intercondylar eminence of the tibia), and down to the center of the
ankle (the ankle mortise, the fork-like grip between the
medial and
lateral malleoli). In the
tibial shaft, the mechanical and anatomical axes coincide, but in the
femoral shaft they diverge 6°, resulting in the
femorotibial angle of 174° in a leg with normal axial alignment. A leg is considered straight when, with the feet brought together, both the medial malleoli of the ankle and the medial condyles of the knee are touching. Divergence from the normal femorotibial angle is called
genu varum if the center of the knee joint is lateral to the mechanical axis (intermalleolar distance exceeds 3 cm), and
genu valgum if it is medial to the mechanical axis (intercondylar distance exceeds 5 cm). These conditions impose unbalanced loads on the joints and stretching of either the thigh's adductors and abductors. The angle of inclination formed between the neck and shaft of the femur (collodiaphysial angle) varies with age—about 150° in the newborn, it gradually decreases to 126–128° in adults, to reach 120° in old age. Pathological changes in this angle result in abnormal posture of the leg: a small angle produces
coxa vara and a large angle
coxa valga; the latter is usually combined with genu varum, and coxa vara leads genu valgum. Additionally, a line drawn through the femoral neck superimposed on a line drawn through the femoral condyles forms an angle, the
torsion angle, which makes it possible for flexion movements of the hip joint to be transposed into rotary movements of the femoral head. Abnormally increased torsion angles result in a limb turned inward and a decreased angle in a limb turned outward; both cases resulting in a reduced range of a person's mobility.
Muscles Hip There are several ways of classifying the muscles of the hip: • By location or innervation (ventral and dorsal divisions of the plexus layer); • By development on the basis of their points of insertion (a posterior group in two layers and an anterior group); and • By function (i.e. extensors, flexors, adductors, and abductors). Some hip muscles also act either on the knee joint or on vertebral joints. Additionally, because the areas of origin and insertion of many of these muscles are very extensive, these muscles are often involved in several very different movements. In the hip joint, lateral and medial rotation occur along the axis of the limb; extension (also called dorsiflexion or retroversion) and flexion (anteflexion or anteversion) occur along a transverse axis; and abduction and adduction occur about a
sagittal axis. The posterior dorsal hip muscles are inserted on or directly below the
greater trochanter of the femur. The
tensor fasciae latae, stretching from the
anterior superior iliac spine down into the
iliotibial tract, presses the
head of the femur into the
acetabulum but also flexes, rotates medially, and abducts to hip joint. The
piriformis originates on the anterior pelvic surface of the
sacrum, passes through the
greater sciatic foramen, and inserts on the posterior aspect of the tip of the greater trochanter. In a standing posture it is a lateral rotator, but it also assists extending the thigh. The
gluteus maximus has its origin between (and around) the
iliac crest and the
coccyx, from where one part radiates into the iliotibial tract and the other stretches down to the
gluteal tuberosity under the greater trochanter. The gluteus maximus is primarily an extensor and lateral rotator of the hip joint, and it comes into action when climbing stairs or rising from a sitting to a standing posture. Furthermore, the part inserted into the fascia latae abducts and the part inserted into the gluteal tuberosity adducts the hip. The two deep glutei muscles, the
gluteus medius and
minimus, originate on the lateral side of the pelvis. The medius muscle is shaped like a cap. Its anterior fibers act as a medial rotator and flexor; the posterior fibers as a lateral rotator and extensor; and the entire muscle abducts the hip. The minimus has similar functions and both muscles are inserted onto the greater trochanter. The ventral hip muscles function as lateral rotators and play an important role in the control of the body's balance. Because they are stronger than the medial rotators, in the normal position of the leg, the apex of the foot is pointing outward to achieve better support. The
obturator internus originates on the pelvis on the
obturator foramen and its
membrane, passes through the
lesser sciatic foramen, and is inserted on the
trochanteric fossa of the femur. "Bent" over the
lesser sciatic notch, which acts as a fulcrum, the muscle forms the strongest lateral rotators of the hip together with the gluteus maximus and quadratus femoris. When sitting with the knees flexed it acts as an abductor. The
obturator externus has a parallel course with its origin located on the posterior border of the obturator foramen. It is covered by several muscles and acts as a lateral rotator and a weak adductor. The
inferior and
superior gemelli muscles represent marginal heads of the obturator internus and assist this muscle. These three muscles form a three-headed muscle (tricipital) known as the
triceps coxae. The
quadratus femoris originates at the
ischial tuberosity and is inserted onto the
intertrochanteric crest between the trochanters. This flattened muscle act as a strong lateral rotator and adductor of the thigh. The
adductor muscles of the thigh are innervated by the
obturator nerve, with the exception of
pectineus which receives fibers from the
femoral nerve, and the
adductor magnus which receives fibers from the
tibial nerve. The
gracilis arises from near the
pubic symphysis and is unique among the adductors in that it reaches past the knee to attach on the medial side of the
shaft of the tibia, thus acting on two joints. It share its distal insertion with the
sartorius and
semitendinosus, all three muscles forming the
pes anserinus. It is the most medial muscle of the adductors, and with the thigh abducted its origin can be clearly seen arching under the skin. With the knee extended, it adducts the thigh and flexes the hip. The
pectineus has its origin on the
iliopubic eminence laterally to the gracilis and, rectangular in shape, extends obliquely to attach immediately behind the lesser trochanter and down the
pectineal line and the proximal part of the
Linea aspera on the femur. It is a flexor of the hip joint, and an adductor and a weak medial rotator of the thigh. The
adductor brevis originates on the
inferior ramus of the pubis below the gracilis and stretches obliquely below the pectineus down to the upper third of the Linea aspera. Except for being an adductor, it is a lateral rotator and weak flexor of the hip joint. The
adductor longus has its origin at
superior ramus of the pubis and inserts medially on the middle third of the Linea aspera. Primarily an adductor, it is also responsible for some flexion. The
adductor magnus has its origin just behind the longus and lies deep to it. Its wide belly divides into two parts: One is inserted into the Linea aspera and the tendon of the other reaches down to
adductor tubercle on the medial side of the femur's distal end where it forms an intermuscular septum that separates the flexors from the extensors. Magnus is a powerful adductor, especially active when crossing legs. Its superior part is a lateral rotator but the inferior part acts as a medial rotator on the flexed leg when rotated outward and also extends the hip joint. The
adductor minimus is an incompletely separated subdivision of the adductor magnus. Its origin forms an anterior part of the magnus and distally it is inserted on the Linea aspera above the magnus. It acts to adduct and lateral rotate the femur.
Thigh The muscles of the
thigh can be classified into three groups according to their location: anterior and posterior muscles and the adductors (on the medial side). All the adductors except gracilis insert on the femur and act on the hip joint, and so functionally qualify as hip muscles. The majority of the thigh muscles, the "true" thigh muscles, insert on the leg (either the tibia or the fibula) and act primarily on the knee joint. Generally, the extensors lie on anterior of the thigh and flexors lie on the posterior. Even though the sartorius flexes the knee, it is
ontogenetically considered an extensor since its displacement is secondary. :
biceps femoris,
semimembranosus, and
semitendinosus muscles.|left There are three main posterior thigh muscles (the
biceps femoris, the
semimembranosus, and the
semitendinosus) collectively known as the
hamstring. The semitendinosus and the semimembranosus share their origin with the long head of the biceps (
the ischial tuberosity), and both attaches on the medial side of the proximal head of the tibia together with the
gracilis and
sartorius to form the
pes anserinus. The semitendinosus acts on two joints; extension of the hip, flexion of the knee, as well as medial rotation of the leg. Distally, the semimembranosus' tendon is divided into three parts referred to as the
pes anserinus profondus. Functionally, the semimembranosus is similar to the semitendinosus, and thus produces extension at the hip joint and flexion and medial rotation at the knee. The biceps femoris has two heads: • The long head has its origin on the ischial tuberosity together with the semitendinosus and acts on two joints. • The short head originates from the middle third of the
linea aspera on the shaft of the femur and the
lateral intermuscular septum of thigh, and acts on only one joint, the knee. It does not have the same point of origin that the hamstring muscles have, and there are some views that the short head is separate to the hamstring. It is depicted as the pink muscle (fourth muscle) in the rotating image of the hamstring in the section. These two heads unite to form the biceps which inserts on the
head of the fibula. The biceps flexes the knee joint and rotates the flexed leg laterally—it is the only
lateral rotator of the knee and thus has to oppose all
medial rotator. Additionally, the long head extends the hip joint. File:Músculo biceps femoral.png|
Biceps femoris File:Semitendinosus.png|
Semitendinosus muscle File:Semimembranosus.gif|
Semimembranosus muscle File:Popliteus large.gif|
Popliteus muscle Posteriorly below the knee joint, the
popliteus muscle stretches obliquely from the
lateral femoral epicondyle down to the posterior surface of the tibia. The
subpopliteal bursa is located deep to the muscle. Popliteus flexes the knee joint and medially rotates the leg.
Lower leg and foot With the
popliteus (see above) as the single exception, all muscles in the leg are attached to the foot and, based on location, can be classified into an anterior and a posterior group separated from each other by the tibia, the fibula, and the
interosseous membrane. In turn, these two groups can be subdivided into subgroups or layers—the anterior group consists of the extensors and the peroneals, and the posterior group of a superficial and a deep layer. Functionally, the muscles of the leg are either extensors, responsible for the
dorsiflexion of the foot, or flexors, responsible for the
plantar flexion. These muscles can also classified by innervation, muscles supplied by the
anterior subdivision of the plexus and those supplied by the
posterior subdivision. The leg muscles acting on the foot are called the extrinsic foot muscles whilst the foot muscles located
in the foot are called intrinsic. Dorsiflexion (extension) and plantar flexion occur around the transverse axis running through the ankle joint from the tip of the medial malleolus to the tip of the lateral malleolus. Pronation (eversion) and supination (inversion) occur along the oblique axis of the ankle joint. Two muscles on the lateral side of the leg form the fibular (peroneal) group. The
fibularis (peroneus) longus and
fibularis (peroneus) brevis both have their origins on the fibula, and they both pass behind the
lateral malleolus where their tendons pass under the
fibular retinacula. Under the foot, the fibularis longus stretches from the lateral to the medial side in a groove, thus bracing the
transverse arch of the foot. The fibularis brevis is attached on the lateral side to the tuberosity of the fifth metatarsal. Together, these two
fibularis muscles form the strongest pronators of the foot. The fibularis muscles are highly variable, and several variants can occasionally be present. Of the posterior muscles three are in the superficial layer. The major plantar flexors, commonly referred to as the
triceps surae, are the
soleus, which arises on the proximal side of both leg bones, and the
gastrocnemius, the two heads of which arises on the distal end of the femur. These muscles unite in a large terminal tendon, the
Achilles tendon, which is attached to the posterior tubercle of the
calcaneus. The
plantaris closely follows the lateral head of the gastrocnemius. Its tendon runs between those of the soleus and gastrocnemius and is embedded in the medial end of the calcaneus tendon. In the deep layer, the
tibialis posterior has its origin on the interosseus membrane and the neighbouring bone areas and runs down behind the
medial malleolus. Under the foot it splits into a thick medial part attached to the
navicular bone and a slightly weaker lateral part inserted to the three cuneiform bones. The muscle produces simultaneous plantar flexion and supination in the non-weight-bearing leg, and approximates the heel to the calf of the leg. The
flexor hallucis longus arises distally on the fibula and on the interosseus membrane from where its relatively thick muscle belly extends far distally. Its tendon extends beneath the
flexor retinaculum to the sole of the foot and finally attaches on the base of the last phalanx of the hallux. It plantarflexes the hallux and assists in supination. The
flexor digitorum longus, finally, has its origin on the upper part of the tibia. Its tendon runs to the sole of the foot where it forks into four terminal tendon attached to the last phalanges of the four lateral toes. It crosses the tendon of the tibialis posterior distally on the tibia, and the tendon of the flexor hallucis longus in the sole. Distally to its division, the
quadratus plantae radiates into it and near the middle phalanges its tendons penetrate the tendons of the
flexor digitorum brevis. In the non-weight-bearing leg, it plantar flexes the toes and foot and supinates. In the weight-bearing leg it supports the
plantar arch. The plantar muscles can be subdivided into three groups associated with three regions: those of the big digit, the little digit, and the region between these two. All these muscles are covered by the thick and dense
plantar aponeurosis, which together with two tough septa, form the spaces of the three groups. These muscles and their fatty tissue function as cushions that transmit the weight of the body downward. As a whole, the foot is a functional entity. The
abductor hallucis stretches along the medial edge of the foot, from the calcaneus to the base of the first phalanx of the first digit and the medial sesamoid bone. It is an abductor and a weak flexor, and also helps maintain the arch of the foot. Lateral to the abductor hallucis is the
flexor hallucis brevis, which originates from the medial cuneiform bone and from the tendon of the tibialis posterior. The flexor hallucis has a medial and a lateral head inserted laterally to the abductor hallucis. It is an important plantar flexor which comes into prominent use in
classical ballet (i.e. for
pointe work). The
opponens digiti minimi originates from the long plantar ligament and the plantar tendinous sheath of the fibularis (peroneus) longus and is inserted on the fifth metatarsal. When present, it acts to plantar flex the fifth digit and supports the plantar arch. The
flexor digiti minimi arises from the region of base of the fifth metatarsal and is inserted onto the base of the first phalanx of the fifth digit where it is usually merged with the abductor of the first digit. It acts to plantar flex the last digit. The largest and longest muscles of the little toe is the
abductor digiti minimi. Stretching from the lateral process of the calcaneus, with a second attachment on the base of the fifth metatarsal, to the base of the fifth digit's first phalanx, the muscle forms the lateral edge of the sole. Except for supporting the arch, it plantar flexes the little toe and also acts as an abductor.
Flexibility Flexibility can be simply defined as the available
range of motion (ROM) provided by a specific
joint or group of joints. For the most part, exercises that increase flexibility are performed with intentions to boost overall muscle length, reduce the risks of injury and to potentially improve muscular performance in
physical activity.
Stretching muscles after engagement in any physical activity can improve muscular strength, increase flexibility, and reduce
muscle soreness. If limited movement is present within a joint, the "insufficient extensibility" of the muscle, or muscle group, could be restricting the activity of the affected joint.
Stretching Stretching prior to strenuous physical activity has been thought to increase muscular performance by extending the soft tissue past its attainable length in order to increase range of motion. Standing heel raises allow the individual to activate their
calf muscles by standing on a step with toes and
forefoot, leaving the heel hanging off the step, and
plantar flexing the
ankle joint by raising the heel. This exercise is easily modified by holding on to a nearby rail for balance and is generally repeated 5–10 times. •
Dorsiflexion: In order to stretch the
anterior muscles of the lower leg, crossover shin stretches work well. This motion will stretch the
dorsiflexion muscles, mainly the
anterior tibialis,
extensor hallucis longus and
extensor digitorum longus, by slowly causing the muscles to lengthen as body weight is leaned on the ankle joint by using the floor as resistance against the top of the foot. The artery enters the thigh as the
femoral artery which descends the medial side of the thigh to the
adductor canal. The canal passes from the anterior to the posterior side of the limb where the artery leaves through the
adductor hiatus and becomes the
popliteal artery. On the back of the knee the popliteal artery runs through the
popliteal fossa to the
popliteal muscle where it divides into
anterior and
posterior tibial arteries. The regions of the hip are all located in the thigh: anteriorly, the subinguinal region is bounded by the inguinal ligament, the sartorius, and the pectineus and forms part of the
femoral triangle which extends distally to the adductor longus. Posteriorly, the gluteal region corresponds to the gluteus maximus. The anterior region of the thigh extends distally from the femoral triangle to the region of the knee and laterally to the tensor fasciae latae. The posterior region ends distally before the popliteal fossa. The anterior and posterior regions of the knee extend from the proximal regions down to the level of the tuberosity of the tibia. In the lower leg the anterior and posterior regions extend down to the malleoli. Behind the malleoli are the lateral and medial retromalleolar regions and behind these is the region of the heel. Finally, the foot is subdivided into a dorsal region superiorly and a plantar region inferiorly. Superficial veins: •
Great saphenous vein •
Small saphenous Deep veins: •
Femoral vein, whose segment is the
common femoral vein •
Popliteal vein •
Anterior tibial vein •
Posterior tibial vein •
Fibular vein Nerve supply The sensory and motor innervation to the lower limb is supplied by the
lumbosacral plexus, which is formed by the
ventral rami of the lumbar and sacral spinal nerves with additional contributions from the
subcostal nerve (T12) and
coccygeal nerve (Co1). Based on distribution and topography, the lumbosacral plexus is subdivided into the
lumbar plexus (T12-L4) and the
Sacral plexus (L5-S4); the latter is often further subdivided into the
sciatic and
pudendal plexuses: The lumbar plexus is formed lateral to the
intervertebral foramina by the ventral rami of the first four lumbar spinal nerves (L1-L4), which all pass through
psoas major. The larger branches of the plexus exit the muscle to pass sharply downward to reach the
abdominal wall and the thigh (under the
inguinal ligament); with the exception of the
obturator nerve which pass through the
lesser pelvis to reach the medial part of the thigh through the
obturator foramen. The nerves of the lumbar plexus pass in front of the
hip joint and mainly support the anterior part of the thigh. The
genitofemoral nerve (L1, L2) leaves psoas major below the two former nerves, immediately divides into two branches that descends along the muscle's anterior side. The sensory femoral branch supplies the skin below the inguinal ligament, while the mixed genital branch supplies the skin and muscles around the sex organ. The
lateral femoral cutaneous nerve (L2, L3) leaves psoas major laterally below the previous nerve, runs obliquely and laterally downward above the
iliacus, exits the pelvic area near the
iliac spine, and supplies the skin of the anterior thigh. The
femoral nerve (L2-L4) is the largest and longest of the nerves of the lumbar plexus. It supplies motor innervation to
iliopsoas,
pectineus,
sartorius, and
quadriceps; and sensory branches to the anterior thigh, medial lower leg, and posterior foot. The
sciatic nerve (L4-S3), the largest and longest nerve in the human body, leaves the pelvis through the
greater sciatic foramen. In the posterior thigh it first gives off branches to the short head of the
biceps femoris and then divides into the
tibial (L4-S3) and
common fibular nerves (L4-S2). The fibular nerve continues down on the medial side of biceps femoris, winds around the fibular neck and enters the front of the lower leg. There it divides into a
deep and a
superficial terminal branch. The superficial branch supplies the
fibularis muscles and the deep branch enters the extensor compartment; both branches reaches into the dorsal foot. In the thigh, the tibial nerve gives off branches to
semitendinosus,
semimembranosus,
adductor magnus, and the long head of the biceps femoris. The nerve then runs straight down the back of the leg, through the
popliteal fossa to supply the ankle flexors on the back of the lower leg and then continues down to supply all the muscles in the sole of the foot. The
pudendal nerve (S2-S4) and
coccygeal plexus (S5-Co) supply the muscles of the
pelvic floor and the surrounding skin. The
lumbosacral trunk is a communicating branch passing between the sacral and lumbar plexuses containing ventral fibers from L4. The
coccygeal nerve, the last spinal nerve, emerges from the
sacral hiatus, unites with the ventral rami of the two last sacral nerves, and forms the
coccygeal plexus. == Lower leg and foot ==