OVERVIEW OF LOWER LIMB

DEVELOPMENT OF LOWER LIMB

BONES OF LOWER LIMB

Arrangement of Lower Limb Bones

Hip Bone

Femur

Tibia and Fibula

Bones of Foot

Surface Anatomy of Bones of Foot

BLUE BOX: Bones of Lower Limb. Lower Limb Injuries; Injuries of Hip Bone; Coxa Vara and Coxa Valga; Dislocated Epiphysis of Femoral Head; Femoral Fractures; Tibial Fractures; Fractures Involving Epiphysial Plates; Fibular Fractures; Bone Grafts; Calcaneal Fractures; Fractures of Talar Neck; Fractures of Metatarsals; Os Trigonum; Fracture of Sesamoid Bones

FASCIA, VEINS, LYMPHATICS, EFFERENT VESSELS, AND CUTANEOUS NERVES OF LOWER LIMB

Subcutaneous Tissue and Fascia

Venous Drainage of Lower Limb

Lymphatic Drainage of Lower Limb

Cutaneous Innervation of Lower Limb

TABLE 5.1. Cutaneous Nerves of Lower Limb

Motor Innervation of Lower Limb

BLUE BOX: Fascia, Veins, Lymphatics, and Cutaneous Nerves of Lower Limb. Compartment Syndromes and Fasciotomy; Varicose Veins, Thrombosis, and Thrombophlebitis; Saphenous Vein Grafts; Saphenous Cutdown and Saphenous Nerve Injury; Enlarged Inguinal Lymph Nodes; Regional Nerve Blocks of Lower Limbs; Abnormalities of Sensory Function

POSTURE AND GAIT

Standing at Ease

Walking: The Gait Cycle

TABLE 5.2. Muscle Action During Gait Cycle

ANTERIOR AND MEDIAL REGIONS OF THIGH

Organization of Proximal Lower Limb

Anterior Thigh Muscles

TABLE 5.3.I. Muscles of Anterior Thigh: Flexors of Hip Joint

TABLE 5.3.II. Muscles of Anterior Thigh: Extensors of Knee

Medial Thigh Muscles

TABLE 5.4. Muscles of Medial Thigh: Adductors of Thigh

Neurovascular Structures and Relationships in Anteromedial Thigh

TABLE 5.5. Arteries of Anterior and Medial Thigh

Surface Anatomy of Anterior and Medial Regions of Thigh

BLUE BOX: Anterior and Medial Regions of Thigh. Hip and Thigh Contusions; Psoas Abscess; Paralysis of Quadriceps; Chondromalacia Patellae; Patellar Fractures; Abnormal Ossification of Patella; Patellar Tendon Reflex; Transplantation of Gracilis; Groin Pull; Injury to Adductor Longus; Palpation, Compression, and Cannulation of Femoral Artery; Laceration of Femoral Artery; Potentially Lethal Misnomer; Saphenous Varix; Location of Femoral Vein; Cannulation of Femoral Vein; Femoral Hernias; Replaced or Accessory Obturator Artery

GLUTEAL AND POSTERIOR THIGH REGIONS

Gluteal Region: Buttocks and Hip Region

Muscles of Gluteal Region

TABLE 5.6. Muscles of Gluteal Region: Abductors and Rotators of Thigh

Posterior Thigh Region

TABLE 5.7. Muscles of Posterior Thigh: Extensors of Hip and Flexors of Knee

Neurovascular Structures of Gluteal and Posterior Thigh Regions

TABLE 5.8. Nerves of Gluteal and Posterior Thigh Regions

TABLE 5.9. Arteries of Gluteal and Posterior Thigh Regions

Surface Anatomy of Gluteal and Posterior Thigh Regions

BLUE BOX: Gluteal and Posterior Thigh Regions. Trochanteric Bursitis; Ischial Bursitis; Hamstring Injuries; Injury to Superior Gluteal Nerve; Anesthetic Block of Sciatic Nerve; Injury to Sciatic Nerve; Intragluteal Injections

POPLITEAL FOSSA AND LEG

Popliteal Region

Anterior Compartment of Leg

TABLE 5.10. Muscles of Anterior and Lateral Compartments of Leg

TABLE 5.11. Nerves of Leg

TABLE 5.12. Arteries of Leg/594

Lateral Compartment of Leg

Posterior Compartment of Leg

TABLE 5.13.I. Superficial Muscles of Posterior Compartment of Leg

TABLE 5.13.II. Deep Muscles of Posterior Compartment of Leg

Surface Anatomy of Leg

BLUE BOX: Popliteal Fossa and Leg. Popliteal Abscess and Tumor; Popliteal Pulse; Popliteal Aneurysm and Hemorrhage; Injury to Tibial Nerve; Containment and Spread of Compartmental Infections in the Leg; Tibialis Anterior Strain (Shin Splints); Fibularis Muscles and Evolution of the Human Foot; Injury to Common Fibular Nerve and Footdrop; Deep Fibular Nerve Entrapment; Superficial Fibular Nerve Entrapment; Fabella in Gastrocnemius; Calcaneal Tendinitis; Ruptured Cancaneal Tendon; Calcaneal Tendon Reflex; Absence of Plantarflexion; Gastrocnemius Strain; Calcaneal Bursitis; Venous Return From Leg; Accessory Soleus; Posterior Tibial Pulse

FOOT

Skin and Fascia of Foot

Muscles of Foot

TABLE 5.14.I. Muscles of Foot: 1st and 2nd Layers of Sole

TABLE 5.14.II. Muscles of Foot: 3rd and 4th Layers of Sole

TABLE 5.14.III. Muscles of Foot: Dorsum of Foot

Neurovascular Structures and Relationships in Foot

TABLE 5.15. Nerves of Foot

Surface Anatomy of Ankle and Foot Regions

BLUE BOX: Foot. Plantar Fasciitis; Infections of Foot; Contusion of Extensor Digitorum Brevis; Sural Nerve Grafts; Anesthetic Block of Superficial Fibular Nerve; Plantar Reflex; Medial Plantar Nerve Entrapment; Palpation of Dorsalis Pedis Pulse; Hemorrhaging Wounds of Sole of Foot; Lymphadenopathy

JOINTS OF LOWER LIMB

Hip Joint

Knee Joint

TABLE 5.16. Movements of Knee Joint and Muscles Producing Them

Tibiofibular Joints

TABLE 5.17. Bursae Around Knee Joint

Ankle Joint

Foot Joints

TABLE 5.18. Joints of Foot

TABLE 5.19. Movements of Joints of Forefoot and Muscles Producing Them

Surface Anatomy of Joints of Knee, Ankle, and Foot

BLUE BOX: Joints of Lower Limb. Bipedalism and Congruity of Articular Surfaces of Hip Joint; Fractures of Femoral Neck; Surgical Hip Replacement; Necrosis of Femoral Head in Children; Dislocation of Hip Joint; Genu Valgum and Genu Varum; Patellar Dislocation; Patellofemoral Syndrome; Knee Joint Injuries; Arthroscopy of Knee Joint; Aspiration of Knee Joint; Bursitis in Knee Region; Popliteal Cysts; Knee Replacement; Ankle Injuries; Tibial Nerve Entrapment; Hallux Valgus; Hammer Toe; Claw Toes; Pes Planus (Flatfeet); Clubfoot (Talipes equinovarus)

OVERVIEW OF LOWER LIMB

The lower limbs (extremities) are extensions from the trunk specialized to support body weight, for locomotion (the ability to move from one place to another), and to maintain balance.

The lower limbs have six major regions (Fig. 5.1):

1.  The gluteal region (G. gloutos, buttocks) is the transitional region between the trunk and free lower limbs. It includes two parts of the lower limb: the rounded, prominent posterior region, the buttocks (L. nates, clunes), and the lateral, usually less prominent hip region (L. regio coxae), which overlies the hip joint and greater trochanter of the femur. The “width of the hips” in common terminology is a reference to one’s transverse dimensions at the level of the greater trochanters. The gluteal region is bounded superiorly by the iliac crest, medially by the intergluteal cleft (natal cleft), and inferiorly by the skin fold (groove) underlying the buttocks, the gluteal fold (L. sulcus glutealis). The gluteal muscles, overlying the pelvic girdle, constitute the bulk of this region.

2.  The femoral region (thigh) is the region of the free lower limb that lies between the gluteal, abdominal, and perineal regions proximally and the knee region distally. It includes most of the femur (thigh bone). The transition from trunk to free lower limb occurs abruptly in the inguinal region or groin. Here the boundary between the abdominal and perineal regions and the femoral region is demarcated by the inguinal ligament anteriorly and the ischiopubic ramus of the hip bone (part of the pelvic girdle or skeleton of the pelvis) medially. Posteriorly, the gluteal fold separates the gluteal and femoral regions (see Fig. 5.46A).

3.  The knee region (L. regio genus) includes the prominences (condyles) of the distal femur and proximal tibia, the head of the fibula, and the patella (knee cap, which lies anterior to the distal end of the femur), as well as the joints between these bony structures. The posterior region of the knee (L. poples) includes a well-defined, fat-filled hollow, transmitting neurovascular structures, called the popliteal fossa.

4.  The leg region (L. regio cruris) is the part that lies between the knee and the narrow, distal part of the leg. It includes most of the tibia (shin bone) and fibula (calf bone). The leg (L., crus) connects the knee and foot. Often laypersons refer incorrectly to the entire lower limb as “the leg.”

5.  The ankle (L. tarsus) or talocrural region (L. regio talocruralis) includes the medial and lateral prominences (malleoli) that flank the ankle (talocrural) joint.

6.  The foot (L. pes) or foot region (L. regio pedis) is the distal part of the lower limb containing the tarsus, metatarsus, and phalanges (toe bones). The toes are the digits of the foot. The great toe (L. hallux), like the thumb, has only two phalanges (digital bones); the other digits have three.

DEVELOPMENT OF LOWER LIMB

Development of the lower limb is illustrated, explained, and contrasted with that of the upper limb in Figure 5.2. Initially, the development of the lower limb is similar to that of the upper limb, although occurring about a week later. During the 5th week, lower limb buds bulge from the lateral aspect of the L2–S2 segments of the trunk (a broader base than for the upper limbs) (Fig. 5.2A). Both limbs initially extend from the trunk with their developing thumbs and great toes directed superiorly and the palms and soles directed anteriorly. Both limbs then undergo torsion around their long axes, but in opposite directions (Fig. 5.2B–D).

The medial rotation and permanent pronation of the lower limb explain how:

•   the knee, unlike the joints superior to it, extends anteriorly and flexes posteriorly, as do the joints inferior to the knee (e.g., interphalangeal joints of the toes);

•   the foot becomes oriented with the great toe on the medial side (Fig. 5.2D), whereas the hand (in the anatomical position) becomes oriented with the thumb on the lateral side; and

•   the “barber-pole” pattern of the segmental innervation of the skin (dermatomes) of the lower limb develops (see “Cutaneous Innervation of Lower Limb,” p. 536).

The torsion and twisting of the lower limb is still in progress at birth (note that babies’ feet tend to meet sole to sole when they are brought together, like clapping). Completion of the process coincides with the mastering of walking skills.

BONES OF LOWER LIMB

The skeleton of the lower limb (inferior appendicular skeleton) may be divided into two functional components: the pelvic girdle and the bones of the free lower limb (Fig. 5.1). The pelvic girdle (bony pelvis) is a bony ring composed of the sacrum and right and left hip bones joined anteriorly at the pubic symphysis.

The pelvic girdle attaches the free lower limb to the axial skeleton, the sacrum being common to the axial skeleton and the pelvic girdle. The pelvic girdle also makes up the skeleton of the lower part of the trunk. Its protective and supportive functions serve the abdomen, pelvis, and perineum as well as the lower limbs. The bones of the free lower limb are contained within and specifically serve that part of the limb.

Arrangement of Lower Limb Bones

Body weight is transferred from the vertebral column through the sacro-iliac joints to the pelvic girdle and from the pelvic girdle through the hip joints to the femurs (L. femora) (Fig. 5.3A). To support the erect bipedal posture better, the femurs are oblique (directed inferomedially) within the thighs so that when standing the knees are adjacent and placed directly inferior to the trunk, returning the center of gravity to the vertical lines of the supporting legs and feet (Figs. 5.1, 5.3, and 5.4). Compare this oblique position of the femurs with that of quadrupeds, in whom the femurs are vertical and the knees are apart, with the trunk mass suspended between the limbs (Fig. 5.3B).

The femurs of human females are slightly more oblique than those of males, reflecting the greater width of their pelves. At the knees, the distal end of each femur articulates with the patella and tibia of the corresponding leg. Weight is transferred from the knee joint to the ankle joint by the tibia. The fibula does not articulate with the femur and does not bear or transfer weight, but it provides for muscle attachment and contributes to the formation of the ankle joint.

At the ankle, the weight borne by the tibia is transferred to the talus (Fig. 5.4). The talus is the keystone of a longitudinal arch formed by the tarsal and metatarsal bones of each foot that distributes the weight evenly between the heel and forefoot when standing, creating a flexible but stable bony platform to support the body.

Hip Bone

The mature hip bone (L. os coxae) is the large, flat pelvic bone formed by the fusion of three primary bones—ilium, ischium, and pubis—at the end of the teenage years. Each of the three bones is formed from its own primary center of ossification; five secondary centers of ossification appear later.

At birth, the three primary bones are joined by hyaline cartilage; in children, they are incompletely ossified (Fig. 5.5). At puberty, the three bones are still separated by a Y-shaped triradiate cartilage centered in the acetabulum, although the two parts of the ischiopubic rami fuse by the 9th year (Fig. 5.5B). The bones begin to fuse between 15 and 17 years of age; fusion is complete between 20 and 25 years of age. Little or no trace of the lines of fusion of the primary bones is visible in older adults (Fig. 5.6). Although the bony components are rigidly fused, their names are still used in adults to describe the three parts of the hip bone.

Because much of the medial aspect of the hip bones/bony pelvis is primarily concerned with pelvic and perineal structures and functions (Chapter 3) or their union with the vertebral column (Chapter 4), it is described more thoroughly in those chapters. Aspects of the hip bones concerned with lower limb structures and functions, mainly involving their lateral aspects, are described in this chapter.

ILIUM

The ilium forms the largest part of the hip bone and contributes the superior part of the acetabulum (Fig. 5.5B). The ilium has thick medial portions (columns) for weight bearing and thin, wing-like, posterolateral portions, the alae (L. wings), that provide broad surfaces for the fleshy attachment of muscles (Fig. 5.3).

The body of the ilium joins the pubis and ischium to form the acetabulum. Anteriorly, the ilium has stout anterior superior and anterior inferior iliac spines that provide attachment for ligaments and tendons of lower limb muscles (Fig. 5.6).

Beginning at the anterior superior iliac spine (ASIS), the long curved and thickened superior border of the ala of the ilium, the iliac crest, extends posteriorly, terminating at the posterior superior iliac spine (PSIS). The crest serves as a protective “bumper” and is an important site of aponeurotic attachment for thin, sheet-like muscles and deep fascia. A prominence on the external lip of the crest, the tubercle of the iliac crest (iliac tubercle), lies 5–6 cm posterior to the ASIS. The posterior inferior iliac spine marks the superior end of the greater sciatic notch.

The lateral surface of the ala of the ilium has three rough curved lines—the posterior, anterior, and inferior gluteal lines—that demarcate the proximal attachments of the three large gluteal muscles (pl., glutei). Medially, each ala has a large, smooth depression, the iliac fossa (Fig. 5.6B), that provides proximal attachment for the iliacus muscle. The bone forming the superior part of this fossa may become thin and translucent, especially in older women with osteoporosis.

Posteriorly, the medial aspect of the ilium has a rough, ear-shaped articular area called the auricular surface (L. auricula, a little ear), and an even rougher iliac tuberosity superior to it for synovial and syndesmotic articulation with the reciprocal surfaces of the sacrum at the sacro-iliac joint.

ISCHIUM

The ischium forms the postero-inferior part of the hip bone. The superior part of the body of the ischium fuses with the pubis and ilium, forming the postero-inferior aspect of the acetabulum. The ramus of the ischium joins the inferior ramus of the pubis to form a bar of bone, the ischiopubic ramus (Fig. 5.6A), which constitutes the inferomedial boundary of the obturator foramen. The posterior border of the ischium forms the inferior margin of a deep indentation called the greater sciatic notch. The large, triangular ischial spine at the inferior margin of this notch provides ligamentous attachment. This sharp demarcation separates the greater sciatic notch from a more inferior, smaller, rounded, and smooth-surfaced indentation, the lesser sciatic notch. The lesser sciatic notch serves as a trochlea or pulley for a muscle that emerges from the bony pelvis. The rough bony projection at the junction of the inferior end of the body of the ischium and its ramus is the large ischial tuberosity. The body’s weight rests on this tuberosity when sitting, and it provides the proximal, tendinous attachment of posterior thigh muscles.

PUBIS

The pubis forms the anteromedial part of the hip bone, contributing the anterior part of the acetabulum, and provides proximal attachment for muscles of the medial thigh. The pubis is divided into a flattened medially placed body and superior and inferior rami that project laterally from the body (Fig. 5.6).

Medially, the symphysial surface of the body of the pubis articulates with the corresponding surface of the body of the contralateral pubis by means of the pubic symphysis (Fig. 5.3A). The anterosuperior border of the united bodies and symphysis forms the pubic crest, which provides attachment for abdominal muscles.

Small projections at the lateral ends of this crest, the pubic tubercles, are important landmarks of the inguinal regions (Fig. 5.6). The tubercles provide attachment for the main part of the inguinal ligament and thereby indirect muscle attachment. The posterior margin of the superior ramus of the pubis has a sharp raised edge, the pecten pubis, which forms part of the pelvic brim (see Chapter 3).

OBTURATOR FORAMEN

The obturator foramen is a large oval or irregularly triangular opening in the hip bone. It is bounded by the pubis and ischium and their rami. Except for a small passageway for the obturator nerve and vessels (the obturator canal), the obturator foramen is closed by the thin, strong obturator membrane. The presence of the foramen minimizes bony mass (weight) while its closure by the obturator membrane still provides extensive surface area on both sides for fleshy muscle attachment.

ACETABULUM

The acetabulum (L., shallow vinegar cup) is the large cup-shaped cavity or socket on the lateral aspect of the hip bone that articulates with the head of the femur to form the hip joint (Fig. 5.6A). All three primary bones forming the hip bone contribute to the formation of the acetabulum (Fig. 5.5).

The margin of the acetabulum is incomplete inferiorly at the acetabular notch, which makes the fossa resemble a cup with a piece of its lip missing (Fig. 5.6A). The rough depression in the floor of the acetabulum extending superiorly from the acetabular notch is the acetabular fossa. The acetabular notch and fossa also create a deficit in the smooth lunate surface of the acetabulum, the articular surface receiving the head of the femur.

ANATOMICAL POSITION OF HIP BONE

Surfaces, borders, and relationships of the hip bone are described assuming that the body is in the anatomical position. To place an isolated hip bone or bony pelvis in this position, situate it so that the:

•   ASIS and the anterosuperior aspect of the pubis lie in the same coronal plane.

•   Symphysial surface of the pubis is vertical, parallel to the median plane (Fig. 5.6).

In the anatomical position, the:

•   Acetabulum faces inferolaterally, with the acetabular notch directed inferiorly.

•   Obturator foramen lies inferomedial to the acetabulum.

•   Internal aspect of the body of the pubis faces almost directly superiorly. (It essentially forms a floor on which the urinary bladder rests.)

•   Superior pelvic aperture (pelvic inlet) is more vertical than horizontal; in the anteroposterior (AP) view, the tip of the coccyx appears near its center (Fig. 5.3).

Femur

The femur is the longest and heaviest bone in the body. It transmits body weight from the hip bone to the tibia when a person is standing (Fig. 5.4). Its length is approximately a quarter of the person’s height. The femur consists of a shaft (body) and two ends, superior or proximal and inferior or distal (Fig. 5.7).

The superior (proximal) end of the femur consists of a head, neck, and two trochanters (greater and lesser). The round head of the femur makes up two thirds of a sphere that is covered with articular cartilage, except for a medially placed depression or pit, the fovea for the ligament of the head. In early life, the ligament gives passage to an artery supplying the epiphysis of the head. The neck of the femur is trapezoidal, with its narrow end supporting the head and its broader base being continuous with the shaft. Its average diameter is three quarters that of the femoral head.

The proximal femur is “bent” (L-shaped) so that the long axis of the head and neck projects superomedially at an angle to that of the obliquely oriented shaft (Fig. 5.7A & B). This obtuse angle of inclination is greatest (most nearly straight) at birth and gradually diminishes (becomes more acute) until the adult angle is reached (115–140°, averaging 126°) (Fig. 5.7C–E).

The angle of inclination is less in females because of the increased width between the acetabula (a consequence of a wider lesser pelvis) and the greater obliquity of the femoral shaft. The angle of inclination allows greater mobility of the femur at the hip joint because it places the head and neck more perpendicular to the acetabulum in the neutral position. The abductors and rotators of the thigh attach mainly to the apex of the angle (the greater trochanter) so they are pulling on a lever (the short limb of the L) that is directed more laterally than vertically. This provides increased leverage for the abductors and rotators of the thigh, and allows the considerable mass of the abductors of the thigh to be placed superior to the femur (in the gluteal region) instead of lateral to it, freeing the lateral aspect of the femoral shaft to provide an increased area for the fleshy attachment of the extensors of the knee.

The angle of inclination also allows the obliquity of the femur within the thigh, which permits the knees to be adjacent and inferior to the trunk, as explained previously. All of this is advantageous for bipedal walking; however, it imposes considerable strain on the neck of the femur. Consequently, fractures of the femoral neck can occur in older people as a result of a slight stumble if the neck has been weakened by osteoporosis (pathologic reduction of bone mass).

The torsion of the proximal lower limb (femur) that occurred during development does not conclude with the long axis of the superior end of the femur (head and neck) parallel to the transverse axis of the inferior end (femoral condyles). When the femur is viewed superiorly (so that one is looking along the long axis of the shaft), it is apparent that the two axes lie at an angle (the torsion angle, or angle of declination), the mean of which is 7° in males and 12° in females. The torsion angle, combined with the angle of inclination, allows rotatory movements of the femoral head within the obliquely placed acetabulum to convert into flexion and extension, abduction and adduction, and rotational movements of the thigh.

Where the femoral neck and shaft join there are two large, blunt elevations called trochanters (Fig. 5.7A, B, & F). The abrupt, conical and rounded lesser trochanter (G., a runner) extends medially from the posteromedial part of the junction of the neck and shaft to give tendinous attachment to the primary flexor of the thigh (the iliopsoas).

The greater trochanter is a large, laterally placed bony mass that projects superiorly and posteriorly where the neck joins the femoral shaft, providing attachment and leverage for abductors and rotators of the thigh. The site where the neck and shaft join is indicated by the intertrochanteric line, a roughened ridge formed by the attachment of a powerful ligament (iliofemoral ligament). The intertrochanteric line runs from the greater trochanter and winds around the lesser trochanter to continue posteriorly and inferiorly as a less distinct ridge, the spiral line.

A similar but smoother and more prominent ridge, the intertrochanteric crest, joins the trochanters posteriorly. The rounded elevation on the crest is the quadrate tubercle. In anterior and posterior views (Fig. 5.7A & B), the greater trochanter is in line with the femoral shaft. In posterior and superior views (Fig. 5.7B & F), it overhangs a deep depression medially, the trochanteric fossa.

The shaft of the femur is slightly bowed (convex) anteriorly. This convexity may increase markedly, proceeding laterally as well as anteriorly, if the shaft is weakened by a loss of calcium, as occurs in rickets (a disease attributable to vitamin D deficiency). Most of the shaft is smoothly rounded, providing fleshy origin to extensors of the knee, except posteriorly where a broad, rough line, the linea aspera, provides aponeurotic attachment for adductors of the thigh. This vertical ridge is especially prominent in the middle third of the femoral shaft, where it has medial and lateral lips (margins). Superiorly, the lateral lip blends with the broad, rough gluteal tuberosity, and the medial lip continues as a narrow, rough spiral line.

The spiral line extends toward the lesser trochanter but then passes to the anterior surface of the femur, where it is continuous with the intertrochanteric line. A prominent intermediate ridge, the pectineal line, extends from the central part of the linea aspera to the base of the lesser trochanter. Inferiorly, the linea aspera divides into medial and lateral supracondylar lines, which lead to the medial and lateral femoral condyles (Fig. 5.7B).

The medial and lateral femoral condyles make up nearly the entire inferior (distal) end of the femur. The two condyles are on the same horizontal level when the bone is in its anatomical position, so that if an isolated femur is placed upright with both condyles contacting the floor or tabletop, the femoral shaft will assume the same oblique position it occupies in the living body (about 9° from vertical in males and slightly greater in females).

The femoral condyles articulate with menisci (crescentic plates of cartilage) and tibial condyles to form the knee joint (Fig. 5.4). The menisci and tibial condyles glide as a unit across the inferior and posterior aspects of the femoral condyles during flexion and extension. The convexity of the articular surface of the condyles increases as it descends the anterior surface, covering the inferior end, and then ascends posteriorly. The condyles are separated posteriorly and inferiorly by an intercondylar fossa but merge anteriorly, forming a shallow longitudinal depression, the patellar surface (Fig. 5.7), which articulates with the patella. The lateral surface of the lateral condyle has a central projection called the lateral epicondyle. The medial surface of the medial condyle has a larger and more prominent medial epicondyle, superior to which another elevation, the adductor tubercle, forms in relation to a tendon attachment. The epicondyles provide proximal attachment for the medial and lateral collateral ligaments of the knee joint.

SURFACE ANATOMY OF PELVIC GIRDLE AND FEMUR

Bony landmarks are helpful during physical examinations and surgery because they can be used to evaluate normal development, detect and assess fractures and dislocations, and locate the sites of structures such as nerves and blood vessels.

When your hands are on your hips, they rest on your iliac crests (Fig. 5.8A). The anterior third of the crests is easily palpated because the crests are subcutaneous (Fig. 5.8C & D). The posterior two thirds of the crests are more difficult to palpate because they are usually covered with fat. The iliac crest ends anteriorly at the rounded ASIS (anterior superior iliac spine), which is easy to palpate by tracing the iliac crest antero-inferiorly. The ASIS is often visible in thin individuals. In obese people these spines are covered with fat and may be difficult to locate; however, they are easier to palpate when the person is sitting and the muscles attached to them are relaxed.

The iliac tubercle, 5–6 cm posterior to the ASIS, marks the widest point of the iliac crest. To palpate this tubercle, place your thumb on the ASIS and move your fingers posteriorly along the external lip of the iliac crest (Fig. 5.8B). The iliac tubercle lies at the level of the spinous process of the L5 vertebra.

Approximately a hand’s width inferior to the umbilicus, the bodies and superior rami of the pubic bones may be palpated (Fig. 5.8C). The pubic tubercle can be palpated about 2 cm from the pubic symphysis at the anterior extremity of the pubic crest. The iliac crest ends posteriorly at the sharp PSIS (posterior superior iliac spine) (Fig. 5.8D), which may be difficult to palpate; however, its position is easy to locate because it lies at the bottom of a skin dimple, approximately 4 cm lateral to the midline. The dimple exists because the skin and underlying fascia attach to the PSIS. The skin dimples are useful landmarks when palpating the area of the sacro-iliac joints in search of edema (swelling) or local tenderness. These dimples also indicate the termination of the iliac crests from which bone marrow and pieces of bone for grafts can be obtained (e.g., to repair a fractured tibia).

The ischial tuberosity is easily palpated in the inferior part of the buttocks when the thigh is flexed (Fig. 5.8E). The buttocks covers and obscures the tuberosity when the thigh is extended (Fig. 5.8D). The gluteal fold coincides with the inferior border of the gluteus maximus and indicates the separation of the buttocks from the thigh.

The center of the femoral head can be palpated deep to a point approximately a thumb’s breadth inferior to the midpoint of the inguinal ligament (Fig. 5.8C). The shaft of the femur is covered with muscles and is not usually palpable. Only the superior and inferior ends of the femur are palpable. The laterally placed greater trochanter projects superior to the junction of the shaft with the femoral neck and can be palpated on the lateral side of the thigh approximately 10 cm inferior to the iliac crest (Fig. 5.8B).

The greater trochanter forms a prominence anterior to the hollow on the lateral side of the buttocks (Fig. 5.8D). The prominences of the greater trochanters are normally responsible for the width of the adult pelvis. The posterior edge of the greater trochanter is relatively uncovered and most easily palpated when the limb is not weight-bearing. The anterior and lateral parts of the trochanter are not easy to palpate because they are covered by fascia and muscle. Because it lies close to the skin, the greater trochanter causes discomfort when you lie on your side on a hard surface. In the anatomical position, a line joining the tips of the greater trochanters normally passes through the pubic tubercles and the center of the femoral heads. The lesser trochanter is indistinctly palpable superior to the lateral end of the gluteal fold.

The femoral condyles are subcutaneous and easily palpated when the knee is flexed or extended (Fig. 5.8C & D). At the center of the lateral aspect of each condyle is a prominent epicondyle that is easily palpable. The patellar surface of the femur is where the patella slides during flexion and extension of the leg at the knee joint. The lateral and medial margins of the patellar surface can be palpated when the leg is flexed. The adductor tubercle, a small prominence of bone, may be felt at the superior part of the medial femoral condyle by pushing your thumb inferiorly along the medial side of the thigh until it encounters the tubercle.

Tibia and Fibula

The tibia and fibula are the bones of the leg (Figs. 5.4 and 5.9). The tibia articulates with the condyles of the femur superiorly and the talus inferiorly, and in so doing transmits the body’s weight. The fibula mainly functions as an attachment for muscles, but it is also important for the stability of the ankle joint. The shafts of the tibia and fibula are connected by a dense interosseous membrane composed of strong oblique fibers descending from the tibia to the fibula.

TIBIA

Located on the anteromedial side of the leg, nearly parallel to the fibula, the tibia (shin bone) is the second largest bone in the body. It flares outward at both ends to provide an increased area for articulation and weight transfer. The superior (proximal) end widens to form medial and lateral condyles that overhang the shaft medially, laterally, and posteriorly, forming a relatively flat superior articular surface, or tibial plateau. This plateau consists of two smooth articular surfaces (the medial one slightly concave and the lateral one slightly convex) that articulate with the large condyles of the femur. The articular surfaces are separated by an intercondylar eminence formed by two intercondylar tubercles (medial and lateral) flanked by relatively rough anterior and posterior intercondylar areas.

The tubercles fit into the intercondylar fossa between the femoral condyles (Fig. 5.7B). The intercondylar tubercles and areas provide attachment for the menisci and principal ligaments of the knee, which hold the femur and tibia together, maintaining contact between their articular surfaces.

The anterolateral aspect of the lateral tibial condyle bears an anterolateral tibial tubercle (Gerdy tubercle) inferior to the articular surface (Fig. 5.9A), which provides the distal attachment for a dense thickening of the fascia covering the lateral thigh, adding stability to the knee joint. The lateral condyle also bears a fibular articular facet posterolaterally on its inferior aspect for the head of the fibula.

Unlike that of the femur, the shaft of the tibia is truly vertical within the leg. It is somewhat triangular in cross-section, having three surfaces and borders: medial, lateral/interosseous, and posterior.

The anterior border of the tibia is the most prominent border. It and the adjacent medial surface are subcutaneous throughout their lengths and are commonly known as the “shin”. Their periosteal covering and overlying skin are vulnerable to bruising. At the superior end of the anterior border, a broad, oblong tibial tuberosity provides distal attachment for the patellar ligament, which stretches between the inferior margin of the patella and the tibial tuberosity.

The tibial shaft is thinnest at the junction of its middle and distal thirds. The distal end of the tibia is smaller than the proximal end, flaring only medially; the medial expansion extends inferior to the rest of the shaft as the medial malleolus. The inferior surface of the shaft and the lateral surface of the medial malleolus articulate with the talus and are covered with articular cartilage (Fig. 5.4).

The interosseous border of the tibia is sharp where it gives attachment to the interosseous membrane that unites the two leg bones (Fig. 5.9). Inferiorly, the sharp border is replaced by a groove, the fibular notch, that accommodates and provides fibrous attachment to the distal end of the fibula.

On the posterior surface of the proximal part of the tibial shaft is a rough diagonal ridge, called the soleal line, which runs inferomedially to the medial border. This line is formed in relationship to the aponeurotic origin of the soleus muscle approximately one third of the way down the shaft. Immediately distal to the soleal line is an obliquely directed vascular groove, which leads to a large nutrient foramen for passage of the main artery supplying the proximal end of the bone and its marrow. From it, the nutrient canal runs inferiorly in the tibia before it opens into the medullary (marrow) cavity.

FIBULA

The slender fibula lies posterolateral to the tibia and is firmly attached to it by the tibiofibular syndesmosis, which includes the interosseous membrane (Fig. 5.9). The fibula has no function in weight-bearing. It serves mainly for muscle attachment, providing distal attachment (insertion) for one muscle and proximal attachment (origin) for eight muscles. The fibers of the tibiofibular syndesmosis are arranged to resist the resulting net downward pull on the fibula.

The distal end enlarges and is prolonged laterally and inferiorly as the lateral malleolus. The malleoli form the outer walls of a rectangular socket (mortise), which is the superior component of the ankle joint (Fig. 5.4A), and provide attachment for the ligaments that stabilize the joint. The lateral malleolus is more prominent and posterior than the medial malleolus and extends approximately 1 cm more distally.

The proximal end of the fibula consists of an enlarged head superior to a small neck (Fig. 5.9). The head has a pointed apex. The head of the fibula articulates with the fibular facet on the posterolateral, inferior aspect of the lateral tibial condyle. The shaft of the fibula is twisted and marked by the sites of muscular attachments. Like the shaft of the tibia, it is triangular in cross-section, having three borders (anterior, interosseous, and posterior) and three surfaces (medial, posterior, and lateral).

SURFACE ANATOMY OF TIBIA AND FIBULA

The tibial tuberosity, an oval elevation on the anterior surface of the tibia, is easily palpated approximately 5 cm distal to the apex of the patella (Fig. 5.10A). The subcutaneous, flat anteromedial surface of the tibia is also easy to palpate. The skin covering this surface is freely movable. The tibial condyles can be palpated anteriorly at the sides of the patellar ligament, especially when the knee is flexed.

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