Mai ka piko o ke poʻo a ka poli o ka wāwae, a lʻa ma na kihi ʻehā o ke kino.

From the crown of the head to the soles of the feet, and the four corners of the body.

An expression used in prayers of healing. The four corners are the shoulders and hips; between them are the vital organs of the body.

‘Ōlelo No‘eau, compiled by Mary Kawena Pukui, #2066

Introduction

Figure 8.1 ʻIwi Kūpuna – Sacred Hawaiian Burials

In the previous chapter, you learned about the bones that make up the axial skeleton. The appendicular skeleton includes the bones that make up your upper limbs (arms) and lower limbs (legs). The axial skeleton is attached to the upper limbs (arms) via the pectoral girdle (shoulder girdle) while the lower limbs (legs) are attached via the pelvic girdle. The pectoral and pelvic girdles are included in the appendicular skeleton.

Figure 8.2: Appendicular Skeleton: Pectoral girdle in purple, upper limb in green, pelvic girdle in blue, and lower limbs in brown.

8.1 Pectoral Girdle

The pectoral girdle is a pair of structures that attach your upper limb to your axial skeleton (Figure 8.2). You have a pectoral girdle on the right and left side of your body. Each pectoral girdle is made up of two bones, the clavicle and scapula (Figure 8.3). The clavicle–anterior part of the pectoral girdle–attaches to the axial skeleton at the manubrium of the sternum, forming the sternoclavicular joint. The scapula is the posterior part of the girdle, held stable against the thoracic cage (rib cage) by muscles, and contains the socket where the humerus of the upper arm attaches to the pectoral girdle. The pectoral girdle is known for its high degree of range of motion, providing humans with significant mobility of the upper limb.

Figure 8.3: Pectoral girdle as it fits on the axial skeleton. Superior and inferior views of the clavicle

Clavicle

The clavicle (collar bone) is located horizontally on the anterior side of the shoulder and can be easily palpated (examined by touch). Although the clavicle is relatively thin compared to the scapula, it has several functions. First, the clavicle is supported by ligaments and muscles to provide lateral support for the scapula. This also creates distance between the shoulder joint and body trunk, allowing a wide range and freedom of motion for the upper limb. The clavicle also helps stabilize movements of the upper limb by transferring forces onto the sternum and axial skeleton. The clavicle also protects underlying nerves and blood vessels passing between the trunk of the body and the upper limb.

The clavicle has three regions: the medial end, the lateral end, and the shaft. The medial end, also referred to as the sternal end, of the clavicle articulates with the manubrium of the sternum. This forms the sternoclavicular joint, which is the only point of articulation between the pectoral girdle of the upper limb and the axial skeleton. This joint allows considerable mobility, enabling the clavicle and scapula to move in superior/inferior and anterior/posterior directions during shoulder movements. The sternoclavicular joint is also indirectly supported by the costoclavicular ligament (costo = rib), which spans the sternal end of the clavicle and the underlying first rib. The lateral end, also known as the acromial end, of the clavicle articulates with the acromion of the scapula, which forms the bony tip of the shoulder.

Extreme forces and trauma can damage the bones of the pectoral girdle. The clavicle is the most commonly fractured bone in the body, and common causes of clavicular fractures include falling onto outstretched arms, or when the shoulder receives a lateral strong blow. Both of these situations can transfer extreme force onto the clavicle. Because the sternoclavicular joint is strong and rarely dislocated, excessive force on the shoulder or arms could result in the clavicle breaking, which usually fractures between the middle and lateral portions of the bone. If the clavicle is completely fractured, the affected pectoral girdle will lose its structural support, and the injured shoulder and lateral clavicle fragment will drop and sag due to the weight of the upper limb and lack of stability, often causing the person to support the sagging limb with their other hand.

Scapula

The scapula (shoulder blade) forms the posterior aspect of the pectoral girdle and is the point of attachment anchoring the upper limb to the body. Despite its appearance on a skeleton, the scapula does not attach or articulate with the ribs of the thoracic cage. Instead, the scapula is held in place by the acromioclavicular joint, ligaments, and muscles that attach to several sites and bone markings on the scapula.

Figure 8.4a: Right scapula and bone markings–anterior and posterior view

Figure 8.4b: Left scapula and bone markings–lateral view

The scapula has numerous landmarks (Figure 8.4). The three margins or borders of the scapula, named for their positions within the body, are the superior border of the scapula, the medial border of the scapula, and the lateral border of the scapula. The suprascapular notch is located lateral to the midpoint of the superior border. The corners of the triangular scapula, at either end of the medial border, are the superior angle of the scapula, located between the medial and superior borders, and the inferior angle of the scapula, located between the medial and lateral borders. The inferior angle is the most inferior portion of the scapula and serves as the attachment point for several powerful muscles involved in shoulder and upper limb movements.

The scapula also has two prominent projections located on the superior and lateral portions of the bone. The acromion, or acromial process, forms the bony tip of the superior shoulder region and articulates with the lateral end of the clavicle, forming the acromioclavicular joint. The coracoid process (coracoid = shaped like a crow’s beak) is a hook-like projection located anterior to the acromion. The coracoid process serves as an attachment site for multiple ligaments and muscles of the anterior chest and arm.

The scapula has three depressions, each of which is called a fossa. Two of these, the supraspinous fossa and infraspinous fossa, are respectively found above and below the scapular spine. On the other side of the scapula, the broad subscapular fossa spans across almost the entire anterior surface of the scapula. These fossae provide large surface areas for attaching muscles that help to stabilize the overall shoulder joint and move the upper limb.

The glenoid cavity, or glenoid fossa, is a relatively smooth indented surface located below the acromion and coracoid processes and between the superior and lateral borders of the scapula. This glenoid cavity forms the socket that receives the head of the humerus bone of the upper arm, which forms the glenohumeral joint (shoulder joint).

8.2 Upper Limb

The upper limb can act as a kinetic chain from the hand, forearm, arm, to the shoulder. FOOSH, short for “fall onto an outstretched hand” is a common way to injure the upper limb. You probably know someone with a FOOSH injury, especially a keiki (child), who fell and automatically reached their hand out to catch themselves. This can lead to problems including but not limited to the hand, but also wrist, elbow, scapula, and clavicle.

Humerus

The humerus is the only bone of the upper arm [Figure 8.5]. The head of the humerus is located at the proximal end of the humerus and inserts into the glenoid cavity of the scapula. The proximal end of the humerus also has smaller bony bumps called the greater tubercle and lesser tubercle, which have a groove (sulcus) between them called the intertubercular groove. The greater and lesser tubercles serve as attachments for muscles of the shoulder joint and arm. The humerus also has two necks. The anatomical neck of the humerus is the border between the smooth head of the humerus and the rest of the humerus. The surgical neck of the humerus is located between the bulbous proximal portion of the humerus and the narrower shaft of the humerus. The deltoid tuberosity is a rough raised area located laterally near the middle of the shaft and serves as the attachment site for the deltoid muscle. This tuberosity is frequently larger and more prominent in people with developed or strong deltoid muscles.

Figure 8.5: Humerus and major bone markings

The distal portion of the humerus closest to the elbow consists of many raised bony projections. These include the trochlea, a spindle- or pulley-shaped region (trochlea = pulley), which is located toward the anterior and medial side of the humerus and is the site of articulation with the ulna. Immediately lateral to the trochlea is the capitulum (small head), a knob-like structure located on the anterior surface of the distal humerus, which articulates with the radius.

The lateral and medial epicondyles of the humerus are located slightly more proximal and towards the medial and lateral sides of the humerus and serve as attachment sites for tendons and ligaments for muscles that move the upper limb.

The distal portion of the humerus also contains multiple depressions that fit projections of the radius and ulna. The coronoid fossa receives the coronoid process of the ulna, the radial fossa above the capitulum receives the head of the radius when the elbow is flexed. Similarly, the posterior humerus has the olecranon fossa, a larger depression that receives the olecranon of the ulna when the forearm is fully extended.

Ulna

The radius and ulna run roughly parallel to each other as the bones of the forearm [Figure 8.6]. If you stand in anatomical position–palms forward and thumbs pointing out and away from your hips–your ulna will be located closer to your torso and the radius will be further away. This places the ulna medial to the radius. The ulna and radius are joined together by the interosseous membrane of the forearm, a sheet of dense connective tissue that helps to hold the two bones together during arm movements.

The olecranon is the proximal part of your ulna and forms the bony point on the back of your elbow that you can palpate while flexing your elbow joint. The olecranon fits in the corresponding olecranon fossa of the humerus. The trochlear notch of the ulna articulates and receives the trochlea of the humerus. The coronoid process of the ulna forms an inferior lip of the trochlear notch and fits into the coronoid fossa of the humerus when the elbow joint flexes. Toward the lateral side of the proximal end of the ulna is the radial notch, which fits the round head of the radius and allows the head of the radius to rotate in place.

The shaft of the ulna runs between the elbow and the wrist, and the interosseous membrane attaches to the interosseous border of the ulna. The head of the ulna is located at the distal end of the ulna closest to the wrist, along with a smaller pointed projection called the styloid process of the ulna.

Figure 8.6: Ulna and radius with major markings

Radius

The head of the radius appears circular when the radius is viewed from its proximal end and articulates with the capitulum of the humerus [Figure 8.6]. The round shape of the radial head also allows the radius to pivot in the radial notch of the ulna and causes the motions seen during supination and pronation of the arm. The neck of the radius is the narrowed region immediately below the expanded head. Inferior to this point on the medial side is the radial tuberosity, an oval-shaped, bony protuberance that serves as a muscle attachment point. The shaft of the radius is slightly curved and has a small ridge along its medial side. This ridge forms the interosseous border of the radius, which, similar to the border of the ulna, is the line of attachment for the interosseous membrane that unites the two forearm bones. The distal end of the radius has a smooth surface for articulation with two carpal bones to form the radiocarpal joint or wrist joint. On the medial side of the distal radius is the ulnar notch of the radius. This shallow depression articulates with the head of the ulna, which together forms the distal radioulnar joint. The lateral end of the radius has a pointed projection called the styloid process of the radius. This provides attachment for ligaments that support the lateral side of the wrist joint. Compared to the styloid process of the ulna, the styloid process of the radius projects more distally, thereby limiting the range of movement for lateral deviations of the hand at the wrist joint.

Carpal Bones

The wrist contains eight carpal bones [Figure 8.7]. These bones form roughly two horizontal rows, with four proximal carpal bones that articulate with your radius and ulna, and four distal carpal bones that articulate with the metacarpal bones located in your palm. Each of the eight carpal bones has a unique name based on its appearance.

The proximal carpal bones, in lateral to medial order, are the scaphoid (boat-shape), lunate (moon-shape), triquetrum (three-cornered), and pisiform (pea-shaped) bones. The small, rounded pisiform bone articulates with the anterior surface of the triquetrum bone. The pisiform thus projects anteriorly, where it forms the bony bump that can be felt at the medial base of your hand. The distal bones, in lateral to medial order, are the trapezium (table), trapezoid (resembles a table), capitate (head-shaped), and hamate (hooked) bones. The hamate bone is characterized by a prominent bony extension on its anterior side called the hook of the hamate bone.

Figure 8.7: Bones of the wrist and hand

The carpal bones, when viewed through a horizontal section of the body, form a broad U-shaped structure [Figure 8.8]. The flexor retinaculum, or transverse carpal ligament, spans the top of the U-shaped structure, creating a space, the carpal tunnel, between the carpal bones and this ligament. The median nerve and flexor tendons of the fingers and thumb run through this tunnel.

Figure 8.8: Carpal Tunnel: Horizontal/cross-section of the carpal tunnel showing the carpal bones, transverse carpal ligament, and median nerve

Metacarpals and Phalanges

The palm of each of your hands contains five metacarpal bones that run between your wrist and your digits (fingers and thumb) [Figure 8.7]. The metacarpal bones are labeled number 1-5 (I-V in Roman numerals), starting laterally with the metacarpal located at your thumb as 1, and counting in order medially toward the little finger (pinky) to end with 5. The proximal ends of the metacarpals form carpometacarpal joints with the carpal bones of your wrist, and the distal ends of the metacarpals form the metacarpophalangeal joints with your fingers and thumb.

The individual bones of your fingers and thumb are collectively called phalanges (singular: phalanx). They are identified based on anatomical direction (proximal, middle, distal phalanges), and numbered similarly to metacarpals–starting with 1 at the manamana lima nui (thumb), and ending with 5 at the manamana iki (little finger). The thumb (pollex) contains only two phalanges: a proximal and distal phalanx. The other four digits have three phalanges each, which is why each of your fingers has three visible segments. The joints between the phalanges in each digit form interphalangeal joints, which, in addition to your metacarpophalangeal joints, are the basis of your knuckles when you make a fist.

8.3 Pelvic Girdle

Coxal Bones, Sacrum, and Coccyx

The pelvic girdle (hip girdle) is formed by a pair of bones called the hip bones or coxal bones (hip bones). Each hip bone serves as the attachment point for each lower limb and firmly attaches to the axial skeleton at the sacrum of the vertebral column. The pubic symphysis unites the right and left hip bones anteriorly. The pelvis is the entire bony structure formed by the two hip bones, the sacrum, and the coccyx [Figure 8.9].

Figure 8.9: The Pelvis

Unlike the bones of the pectoral girdle, which are highly mobile and allow a wide range of upper limb movements in multiple directions, the bones of the pelvis are joined together with strong, largely immobile joints. By limiting movement, the joints of the pelvic girdle form a more robust structure that can support and bear weight better than a looser structure This is critical for stability because it enables the weight of the body to be transferred laterally from the vertebral column, through the pelvic girdle and hip joints, and into the lower limbs. Thus, the immobility of the pelvis and the strong joints that hold it together provide a foundation for the upper body.

Each adult hip bone has three parts, the ilium, ischium, and pubis [Figure 8.10]. Each of these regions starts as separate bones but as you transition from a teenager to an adult they start to fuse and ossify at their common borders. The ilium is the largest and most superior part of each hip bone. The ilium also forms the largely immobile sacroiliac joint with the sacrum, which is the point of attachment of the pelvic girdle to the axial skeleton. In each hip bone’s inferior portion, the ischium forms the posterior part and the pubis forms the anterior part. The medial portion of each pubis is joined together by the pubic symphysis, a tough band of fibrocartilage.

Figure 8.10: The Hip Bone

The ilium, ischium, and pubis also fuse at a common site on each of the hip bones and form the acetabulum, a rounded, concave socket located on the lateral side of each hip bone. The acetabulum (vinegar cup) receives the rounded head of the femur and is the site where each lower limb attaches to the pelvic girdle.

The ilium forms the largest and most superior portion of each hip bone. When you place your hands on your waist, you can feel the hard lateral border of each ilium along your waistline, which is the iliac crest that forms the superior border of each ilium. The iliac crest is a ridge that helps attach multiple ligaments and muscles to the pelvis. The iliac crest also ends at several projections called spines, which serve as attachment sites for various ligaments and muscles. These projections include the anterior superior iliac spine, anterior inferior iliac spine, posterior superior iliac spine, and posterior inferior iliac spine. The inner medial surface of each upper ilium has a shallow depression called the iliac fossa. The recessed, concave surface of the fossa helps to support abdominal organs while also providing a surface for muscle attachment. The posterior margin of each lower ilium also has a large U-shaped indentation called the greater sciatic notch, which allows the sciatic nerve, other nerves, muscles, and blood vessels to pass through the pelvis as they run between the trunk of the body and the lower limbs.

The ischium forms the inferior, posterior, and lateral portions of each hip bone. The ischial tuberosity is a large, roughened area of the inferior ischium. The ischial tuberosity serves as the attachment site for posterior thigh muscles and also supports the weight of your body when sitting. If you’re sitting in a hard chair and move around in it, you may feel the ischial tuberosity being pressed against the seat of your chair. The slightly curved posterior margin of the ischium above the ischial tuberosity is the lesser sciatic notch. The ischial spine is a bony projection located between the lesser sciatic notch of the ischium and the greater sciatic notch of the ilium. The ischial ramus projects superiorly and anteriorly from the ischial tuberosity and joins the ischium with the pubis at the ischiopubic ramus.

The pubis forms the anterior portion of the hip bone, and fuses with the ilium at its superolateral border. The superior pubic ramus is the segment of bone that passes laterally from the pubic body to join the ilium. The narrow ridge running along the superior margin of the superior pubic ramus is the pectineal line of the pubis. The pubis is a roughly angular structure that has a superior ramus and an inferior ramus. The rami of the pubis bones fuse with the ischium to form a round structure called the obturator foramen, which is located on each side of the inferior and anterior portion of the pelvis. A small bump called the pubic tubercle is located on the anterior of each pubis and between the superior and inferior rami.

The left and right pubic bodies are joined by the pubic symphysis. Extending downward and laterally from the body is the inferior pubic ramus. The pubic arch is the bony structure formed by the pubic symphysis, and the bodies and inferior pubic rami of the adjacent pubic bones. The inferior pubic ramus extends downward to join the ischial ramus. Together, these form the single ischiopubic ramus, which extends from the pubic body to the ischial tuberosity. The inverted V-shape formed as the ischiopubic rami from both sides comes together at the pubic symphysis is called the subpubic angle, which is generally wider in females and narrower in males.

The pelvis is also divided into two larger regions. The greater pelvis (false pelvis) is a broad area formed by the flared superior regions of each ilium and is bounded by the iliac crest on each side [Figure 8.11]. The area of the greater pelvis provides space and structural support to the intestinal organs of the abdominal cavity. The lesser pelvis (true pelvis) refers to the space inferior to the pelvic brim, which is delineated by the inner arcuate line located on the medial surface of each iliac region. The lesser pelvis contains the bladder and internal reproductive organs. The pelvic brim is also known as the pelvic inlet, which is the superior border of the lesser pelvis. The inferior border of the lesser pelvis, also known as the pelvic outlet is bounded by the inferior tip of the coccyx, ischial spines, and pubic symphysis.

Figure 8.11: Greater (False) and Lesser (True) Pelves

Comparison of Female and Male Pelves

Adult wahine (female) and kāne (male) pelves differ in size and function. Generally speaking, the bones of the male pelvis are thicker and heavier, with larger surface markings. The greater sciatic notch of the male hip bone is narrower and deeper than the broader notch of females. Because the female pelvis is adapted for childbirth, it is wider than the male pelvis, as evidenced by the distance between the anterior superior iliac spines (Figure 8.12). The ischial tuberosities of females are also farther apart, which increases the size of the pelvic outlet. Because of this increased pelvic width, the subpubic angle of the pubic arch is larger in females (greater than 90 degrees) than it is in males (less than 70 degrees). The female sacrum is wider, shorter, and less curved, and the sacral promontory projects less into the pelvic cavity, thus giving the female pelvic inlet (pelvic brim) a more rounded or oval shape compared to males. The lesser pelvic cavity of females is also wider and more shallow than the narrower, deeper, and tapering lesser pelvis of males. Because of the obvious differences between female and male hip bones, this is the one bone of the body that allows for the most accurate sex determination from a skeleton. Table 8.1 provides an overview of the general differences between the female and male pelvis.

Figure 8.12 Female and Male Pelves The female pelvis is adapted for childbirth and is broader, with a larger subpubic angle, a rounder pelvic brim, and a wider and more shallow lesser pelvic cavity than the male pelvis.

Table 8.1 Overview of Differences between the Female and Male Pelves

8.4 Lower Limbs

The lower limb consists of three major regions, the thigh, the leg (calf and shin), and the foot. Anatomists sometimes draw a distinction between the whole lower limb and what is commonly called a leg by using the terms upper leg for the thigh, and lower leg for the portion that includes the calf and shin. Each lower limb contains a femur, a patella, a tibia, and a fibula, seven tarsal bones, and metatarsals and phalanges of the foot.

Femur

The femur is the longest, strongest, and heaviest bone in your body [Figure 8.13].

Figure 8.13: Femur articulating with the hip bone and knee joint

The smooth spherical head of the femur is the most proximal part of the femur and fits into the acetabulum of the hip bone. At the distal end of the femur, it articulates with the tibia of the lower leg. The neck of the femur joins the long shaft of the femur at an angle, instead of straight along the axis of the shaft. This angle transfers weight from the pelvis onto your two lower limbs, but is also part of the reason why the neck of the femur is the most common site of what are commonly called hip fractures. Despite its name, hip fractures are breaks along the neck of the femur and not a fracture in the actual hip bone. Forty percent of hip fracture sufferers are unable to walk independently a year later. One in four adults who fracture a hip dies within a year. Additionally, we are in need of healthcare reform and increased outreach to address racial and ethnic disparities indicating worse treatment and outcomes for people of color with hip fractures. Low bone density doubles or even triples hip fracture risk, so encourage people in your community to be physically active and eat healthy with plenty of fresh fruits and vegetables.

Kalo Leaf Underside	Kalo Leaves – Cooked in Laulau	Squid lūʻau with Kalo Leaves

Figure 8.14 Kalo (Taro)

Each femur has a greater trochanter and lesser trochanter, which are large, rough projections located on the proximal end of the femur. The greater trochanter protrudes laterally and slightly superiorly, while the lesser trochanter is smaller and projects toward the posterior. Both trochanters anchor large tendons to the femur.

The elongated shaft of the femur has a slight anterior bowing or curvature. At its proximal end, the posterior shaft has the gluteal tuberosity that eventually becomes continuous with the linea aspera (rough line) as you travel distally down the shaft. The linea aspera is notable for attaching several muscles that move the hip.

The distal end of the femur has multiple medial and lateral bony bumps and protrusions. The linea aspera splits into a pair of ridges that become continuous with the medial epicondyle and lateral epicondyle located on their respective sides of the distal end of the femur. The lateral condyle of the femur and medial condyle of the femur are smooth projections that articulate with the tibia to form the knee joint. The epicondyles provide attachment for muscles and supporting ligaments of the knee. Anteriorly, the smooth surfaces of the condyles join together to form a wide groove called the patellar surface, which allows the patella to articulate and glide smoothly over the condyles. The combination of the medial and lateral condyles with the patellar surface gives the distal end of the femur a U shape.

Patella

The patella (kneecap) is the largest sesamoid bone of the body. The patella is found in the tendon of the quadriceps femoris muscle, the large muscle of the anterior thigh that passes across the anterior knee and attaches to the tibia. The patella articulates with the patellar surface of the femur and thus prevents rubbing of the quadriceps femoris muscle-tendon against the femur. The broad end of the patella is called the base and the pointed end is the apex. The patella lifts the tendon away from the knee joint and also acts as a pulley, which increases the leverage power of the quadriceps femoris muscle as it contracts and extends the lower leg at the knee. The patella glides across the anterior surface of the condyles of the femur and does not articulate with the tibia.

Tibia and Fibula

Figure 8.15: Tibia and Fibula

The tibia and fibula run parallel to each other in the lower leg, much like the radius and ulna in the upper limb [Figure 8.15]. The proximal end of the tibia is broad and forms the medial condyle of the tibia and the lateral condyle of the tibia. The top surface of each condyle is smooth and flattened and articulates with the medial and lateral condyles of the femur to form the knee joint. The tibia does not have epicondyles. The intercondylar eminence, an irregular, elevated area that separates the surfaces of the tibial condyles and serves as the inferior attachment point for two supporting ligaments of the knee.

The tibial tuberosity is an elevated area on the anterior side of the tibia, near its proximal end. It is the site of attachment for the tendon of the quadriceps femoris muscle, and you can feel it through your skin. This tendon continues below the patella as the patellar ligament. If you move your hand from the tibial tuberosity and along the anterior surface of your lower leg, you will feel a bony ridge. This ridge is the anterior border of the tibia (shin). The interosseous border of the tibia is another small ridge running down the lateral side of the tibial shaft. The interosseous membrane of the leg is a sheet of dense connective tissue that attaches to the border and holds the tibia and fibula bones together, similar to the interosseous membrane that holds the radius and ulna together in the upper arm.

The distal end of the tibia has a large expansion on the medial side called the medial malleolus (malleolus = little hammer). You can feel this as the large bony bump found on the medial side of your ankle. The smooth inner surface of the medial malleolus and the distal end of the tibia fit and articulate with the talus bone of the foot to form part of the ankle joint. The distal tibia has a wide groove called the fibular notch, which fits the distal end of the fibula.

The fibula is the slender bone located on the lateral side of the leg. The fibula does not articulate with the femur and it does not bear weight. It serves primarily for muscle attachments and thus is largely surrounded by muscles to help stabilize the ankle joint. Only the proximal and distal ends of the fibula can be palpated.

The head of the fibula is the small, knob-like, proximal end of the fibula. It articulates with the inferior aspect of the lateral tibial condyle, forming the proximal tibiofibular joint. The thin shaft of the fibula has the interosseous border of the fibula, a narrow ridge running down its medial side for the attachment of the interosseous membrane that spans the fibula and tibia. The distal end of the fibula forms the lateral malleolus, which forms the easily palpated bony bump on the lateral side of the ankle. The deep, or medial, side of the lateral malleolus articulates with the talus bone of the foot as part of the ankle joint. The distal fibula also articulates with the fibular notch of the tibia.

Figure 8.16 Woman Surfing

Tarsal Bones

The posterior half of the foot is formed by seven tarsal bones [Figure 8.17]. The most superior bone is the talus. This has a relatively square-shaped, upper surface that articulates with the tibia and fibula to form the ankle joint. Three areas of articulation form the ankle joint: The superomedial surface of the talus bone articulates with the medial malleolus of the tibia, the top of the talus articulates with the distal end of the tibia, and the lateral side of the talus articulates with the lateral malleolus of the fibula. Inferiorly, the talus articulates with the calcaneus (heel bone), the largest bone of the foot, which forms the heel. Bodyweight is transferred from the tibia to the talus to the calcaneus, which rests on the ground.

The cuboid bone articulates with the anterior end of the calcaneus bone. The cuboid has a deep groove running across its inferior surface, which provides passage for a muscle tendon. The talus bone articulates anteriorly with the navicular bone, which in turn articulates anteriorly with the three cuneiform (wedge-shaped) bones. These bones are the medial cuneiform, the intermediate cuneiform, and the lateral cuneiform. Each of these bones has a broad superior surface and a narrow inferior surface, which together produce the transverse, or medial-lateral, curvature of the foot. The navicular and lateral cuneiform bones also articulate with the medial side of the cuboid bone.

Figure 8.17 Bones of the Foot The bones of the foot are divided into three groups. The posterior foot is formed by the seven tarsal bones. The mid-foot has five metatarsal bones. The toes contain the phalanges. The left panel shows the superior view, the top right panel shows the medial view, and the bottom right panel shows the lateral view.

Metatarsals

The anterior half of the foot is formed by the five metatarsal bones, which are located between the tarsal bones of the posterior foot and the phalanges of the toes [Figure 8.17]. These elongated bones are numbered 1 to 5, starting with the medial side of the foot. Each metatarsal has a proximal base, a shaft, and a distal head. The first metatarsal bone is shorter and thicker than the others. The second metatarsal is the longest. The base of the metatarsal bone is the proximal end of each metatarsal bone. These articulate with the cuboid or cuneiform bones. The base of the fifth metatarsal has a large, lateral expansion that provides for muscle attachments. This expanded base of the fifth metatarsal can be felt as a bony bump at the midpoint along the lateral border of the foot. The expanded distal end of each metatarsal is the head of the metatarsal bone. Each metatarsal bone articulates with the proximal phalanx of a toe to form a metatarsophalangeal joint. The heads of the metatarsal bones also rest on the ground and form the anterior end, or ball, of the foot.

Lower Phalanges and Hallux

The toes contain a total of 14 phalanx bones, arranged similarly to the phalanges of the fingers. The toes are numbered from 1 to 5, starting with the hallux (big toe) from the medial side. The big toe has two phalanx bones, the proximal and distal phalanges. The remaining toes all have proximal, middle, and distal phalanges. A joint between adjacent phalanx bones is called an interphalangeal joint.

Arches of the Foot

When the foot comes into contact with the ground during walking, running, or jumping activities, the impact of the body weight puts a tremendous amount of pressure and force on the foot. During running, the force applied to each foot as it contacts the ground can be up to 2.5 times your body weight. The bones, joints, ligaments, and muscles of the foot absorb this force, thus greatly reducing the amount of shock that is passed superiorly into the lower limb and body. The arches of the foot play an important role in this shock-absorbing ability. When weight is applied to the foot, these arches will flatten somewhat, thus absorbing energy. When the weight is removed, the arch rebounds, giving spring to the step. The arches also serve to distribute body weight side to side and to either end of the foot.

The foot has a transverse arch, a medial longitudinal arch, and a lateral longitudinal arch. The transverse arch forms the medial-lateral curvature of the midfoot. It is formed by the wedge shapes of the cuneiform bones and bases (proximal ends) of the first to fourth metatarsal bones. This arch helps to distribute body weight from side to side within the foot, thus allowing the foot to accommodate uneven terrain.

The longitudinal arches run down the length of the foot. The lateral longitudinal arch is relatively flat, whereas the medial longitudinal arch is larger and taller. The longitudinal arches are formed by the tarsal bones posteriorly and the metatarsal bones anteriorly. These arches are supported at either end, where they contact the ground. Posteriorly, this support is provided by the calcaneus bone and anteriorly by the heads (distal ends) of the metatarsal bones. The talus bone, which receives the weight of the body, is located at the top of the longitudinal arches. Bodyweight is then conveyed from the talus to the ground by the anterior and posterior ends of these arches. Strong ligaments unite the adjacent foot bones to prevent disruption of the arches during weight-bearing. On the bottom of the foot, additional ligaments tie together the anterior and posterior ends of the arches. These ligaments have elasticity, which allows them to stretch somewhat during weight-bearing, thus allowing the longitudinal arches to spread. The stretching of these ligaments stores energy within the foot, rather than passing these forces into the leg. Contraction of the foot muscles also plays a role in this energy absorption. When the weight is removed, the elastic ligaments recoil and pull the ends of the arches closer together. This recovery of the arches releases the stored energy and improves the energy efficiency of walking.

Stretching of the ligaments that support the longitudinal arches can lead to pain. This can occur in overweight individuals; with people who have jobs that involve standing for long periods; or those who walk or run long distances. If stretching of the ligaments is prolonged, excessive, or repeated, it can result in a gradual lengthening of the supporting ligaments, with subsequent depression or collapse of the longitudinal arches, particularly on the medial side of the foot. This condition is called pes planus or flatfoot (fallen arches). On the other hand, clawfoot is a condition where the medial longitudinal arch is abnormally raised and it can be caused by muscle deformities as may be seen in diabetics.

Figure 8.18: Bunion

Chapter Summary

Sources

Canfield, Mark A.; Mai, Cara T.; Ying Wang; O’Halloran, Alissa; Marengo, Lisa K.; Olney, Richard S.; Borger, Christopher L.; Rutkowski, Rachel; Fornoff, Jane; Irwin, Nila; Copeland, Glenn; Flood, Timothy J.; Meyer, Robert E.; Rickard, Russel; Alverson, C. J.; Sweatlock, Joseph; Kirby, Russell S. American Journal of Public Health. Sep2014, Vol. 104 Issue 9, pe14-e23. 10p. 4 Charts. DOI: 10.2105/AJPH.2014.302098.

Toledo Avelar, L. E., Cardoso, M. A., Santos Bordoni, L., de Miranda Avelar, L., and de Miranda Avelar, J. V. (2017). Aging and Sexual Differences of the Human Skull. Plastic and reconstructive surgery. Global open, 5(4), e1297. https://doi.org/10.1097/GOX.0000000000001297

https://www.bones.nih.gov/health-info/bone/osteoporosis/fracture

Key Terms

acetabulum

large, cup-shaped cavity located on the lateral side of the hip bone; formed by the junction of the ilium, pubis, and ischium portions of the hip bone

acromial process

acromion of the scapula

acromioclavicular joint

articulation between the acromion of the scapula and the acromial end of the clavicle

acromion

flattened bony process that extends laterally from the scapular spine to form the bony tip of the shoulder

small, bony bump located on the superior aspect of the medial epicondyle of the femur

anatomical neck

line on the humerus located around the outside margin of the humeral head

ankle joint

joint that separates the leg and foot portions of the lower limb; formed by the articulations between the talus bone of the foot inferiorly, and the distal end of the tibia, medial malleolus of the tibia, and lateral malleolus of the fibula superiorly

anterior border of the tibia

narrow, anterior margin of the tibia that extends inferiorly from the tibial tuberosity

anterior inferior iliac spine

small, bony projection located on the anterior margin of the ilium, below the anterior superior iliac spine

anterior superior iliac spine

rounded, anterior end of the iliac crest

arm

region of the upper limb located between the shoulder and elbow joints; contains the humerus bone

base of the metatarsal bone

expanded, proximal end of each metatarsal bone

calcaneus

heel bone; posterior, inferior tarsal bone that forms the heel of the foot

capitate

from the lateral side, the third of the four distal carpal bones; articulates with the scaphoid and lunate proximally, the trapezoid laterally, the hamate medially, and primarily with the third metacarpal distally

capitulum

knob-like bony structure located anteriorly on the lateral, distal end of the humerus

carpal bone

one of the eight small bones that form the wrist and base of the hand; these are grouped as a proximal row consisting of (from lateral to medial) the scaphoid, lunate, triquetrum, and pisiform bones, and a distal row containing (from lateral to medial) the trapezium, trapezoid, capitate, and hamate bones

carpal tunnel

passageway between the anterior forearm and hand formed by the carpal bones and flexor retinaculum

carpometacarpal joint

articulation between one of the carpal bones in the distal row and a metacarpal bone of the hand

clavicle

collarbone; elongated bone that articulates with the manubrium of the sternum medially and the acromion of the scapula laterally

coracoid process

short, hook-like process that projects anteriorly and laterally from the superior margin of the scapula

coronoid fossa

depression on the anterior surface of the humerus above the trochlea; this space receives the coronoid process of the ulna when the elbow is maximally flexed

coronoid process of the ulna

projecting bony lip located on the anterior, proximal ulna; forms the inferior margin of the trochlear notch

costoclavicular ligament

band of connective tissue that unites the medial clavicle with the first rib

coxal bone

hip bone

cuboid

tarsal bone that articulates posteriorly with the calcaneus bone, medially with the lateral cuneiform bone, and anteriorly with the fourth and fifth metatarsal bones

deltoid tuberosity

roughened, V-shaped region located laterally on the mid-shaft of the humerus

distal radioulnar joint

articulation between the head of the ulna and the ulnar notch of the radius

elbow joint

joint located between the upper arm and forearm regions of the upper limb; formed by the articulations between the trochlea of the humerus and the trochlear notch of the ulna, and the capitulum of the humerus and the head of the radius

femur

thigh bone; the single bone of the thigh

fibula

thin, non-weight-bearing bone found on the lateral side of the leg

fibular notch

wide groove on the lateral side of the distal tibia for articulation with the fibula at the distal tibiofibular joint

flexor retinaculum

strong band of connective tissue at the anterior wrist that spans the top of the U-shaped grouping of the carpal bones to form the roof of the carpal tunnel

foot

portion of the lower limb located distal to the ankle joint

forearm

region of the upper limb located between the elbow and wrist joints; contains the radius and ulna bones

fossa

(plural = fossae) shallow depression on the surface of a bone

glenohumeral joint

shoulder joint; formed by the articulation between the glenoid cavity of the scapula and the head of the humerus

glenoid cavity

(also, glenoid fossa) shallow depression located on the lateral scapula, between the superior and lateral borders

gluteal tuberosity

roughened area on the posterior side of the proximal femur, extending inferiorly from the base of the greater trochanter

greater pelvis

(also, greater pelvic cavity or false pelvis) broad space above the pelvic brim defined laterally by the fan-like portion of the upper ilium

greater sciatic notch

large, U-shaped indentation located on the posterior margin of the ilium, superior to the ischial spine

greater trochanter

large, bony expansion of the femur that projects superiorly from the base of the femoral neck

greater tubercle

enlarged prominence located on the lateral side of the proximal humerus

hallux

big toe; digit 1 of the foot

hamate

from the lateral side, the fourth of the four distal carpal bones; articulates with the lunate and triquetrum proximally, the fourth and fifth metacarpals distally, and the capitate laterally

hand

region of the upper limb distal to the wrist joint

head of the femur

rounded, proximal end of the femur that articulates with the acetabulum of the hip bone to form the hip joint

head of the fibula

small, knob-like, proximal end of the fibula; articulates with the inferior aspect of the lateral condyle of the tibia

head of the humerus

smooth, rounded region on the medial side of the proximal humerus; articulates with the glenoid fossa of the scapula to form the glenohumeral (shoulder) joint

head of the metatarsal bone

expanded, distal end of each metatarsal bone

head of the radius

disc-shaped structure that forms the proximal end of the radius; articulates with the capitulum of the humerus as part of the elbow joint, and with the radial notch of the ulna as part of the proximal radioulnar joint

head of the ulna

small, rounded distal end of the ulna; articulates with the ulnar notch of the distal radius, forming the distal radioulnar joint

hip bone

coxal bone; single bone that forms the pelvic girdle; consists of three areas, the ilium, ischium, and pubis

hip joint

joint located at the proximal end of the lower limb; formed by the articulation between the acetabulum of the hip bone and the head of the femur

hook of the hamate bone

bony extension located on the anterior side of the hamate carpal bone

humerus

single bone of the upper arm

iliac crest

curved, superior margin of the ilium

iliac fossa

shallow depression found on the anterior and medial surfaces of the upper ilium

ilium

superior portion of the hip bone

inferior angle of the scapula

inferior corner of the scapula located where the medial and lateral borders meet

inferior pubic ramus

narrow segment of bone that passes inferiorly and laterally from the pubic body; joins with the ischial ramus to form the ischiopubic ramus

infraspinous fossa

broad depression located on the posterior scapula, inferior to the spine

intercondylar eminence

irregular elevation on the superior end of the tibia, between the articulating surfaces of the medial and lateral condyles

intermediate cuneiform

middle of the three cuneiform tarsal bones; articulates posteriorly with the navicular bone, medially with the medial cuneiform bone, laterally with the lateral cuneiform bone, and anteriorly with the second metatarsal bone

interosseous border of the fibula

small ridge running down the medial side of the fibular shaft; for attachment of the interosseous membrane between the fibula and tibia

interosseous border of the radius

narrow ridge located on the medial side of the radial shaft; for attachment of the interosseous membrane between the ulna and radius bones

interosseous border of the tibia

small ridge running down the lateral side of the tibial shaft; for attachment of the interosseous membrane between the tibia and fibula

interosseous border of the ulna

narrow ridge located on the lateral side of the ulnar shaft; for attachment of the interosseous membrane between the ulna and radius

interosseous membrane of the forearm

sheet of dense connective tissue that unites the radius and ulna bones

interosseous membrane of the leg

sheet of dense connective tissue that unites the shafts of the tibia and fibula bones

interphalangeal joint

articulation between adjacent phalanx bones of the hand or foot digits

intertubercular groove (sulcus)

bicipital groove; narrow groove located between the greater and lesser tubercles of the humerus

ischial ramus

bony extension projecting anteriorly and superiorly from the ischial tuberosity; joins with the inferior pubic ramus to form the ischiopubic ramus

ischial spine

pointed, bony projection from the posterior margin of the ischium that separates the greater sciatic notch and lesser sciatic notch

ischial tuberosity

large, roughened protuberance that forms the posteroinferior portion of the hip bone; weight-bearing region of the pelvis when sitting

ischiopubic ramus

narrow extension of bone that connects the ischial tuberosity to the pubic body; formed by the junction of the ischial ramus and inferior pubic ramus

ischium

posteroinferior portion of the hip bone

knee joint

joint that separates the thigh and leg portions of the lower limb; formed by the articulations between the medial and lateral condyles of the femur, and the medial and lateral condyles of the tibia

lateral border of the scapula

diagonally oriented lateral margin of the scapula

lateral condyle of the femur

smooth, articulating surface that forms the distal and posterior sides of the lateral expansion of the distal femur

lateral condyle of the tibia

lateral, expanded region of the proximal tibia that includes the smooth surface that articulates with the lateral condyle of the femur as part of the knee joint

lateral cuneiform

most lateral of the three cuneiform tarsal bones; articulates posteriorly with the navicular bone, medially with the intermediate cuneiform bone, laterally with the cuboid bone, and anteriorly with the third metatarsal bone

lateral epicondyle of the femur

roughened area of the femur located on the lateral side of the lateral condyle

lateral malleolus

expanded distal end of the fibula

leg

portion of the lower limb located between the knee and ankle joints

lesser pelvis

(also, lesser pelvic cavity or true pelvis) narrow space located within the pelvis, defined superiorly by the pelvic brim (pelvic inlet) and inferiorly by the pelvic outlet

lesser sciatic notch

shallow indentation along the posterior margin of the ischium, inferior to the ischial spine

lesser trochanter

small, bony projection on the medial side of the proximal femur, at the base of the femoral neck

lesser tubercle

small, bony prominence located on anterior side of the proximal humerus

linea aspera

longitudinally running bony ridge located in the middle third of the posterior femur

lunate

from the lateral side, the second of the four proximal carpal bones; articulates with the radius proximally, the capitate and hamate distally, the scaphoid laterally, and the triquetrum medially

medial border of the scapula

elongated, medial margin of the scapula

medial condyle of the femur

smooth, articulating surface that forms the distal and posterior sides of the medial expansion of the distal femur

medial condyle of the tibia

medial, expanded region of the proximal tibia that includes the smooth surface that articulates with the medial condyle of the femur as part of the knee joint

medial cuneiform

most medial of the three cuneiform tarsal bones; articulates posteriorly with the navicular bone, laterally with the intermediate cuneiform bone, and anteriorly with the first and second metatarsal bones

medial malleolus

bony expansion located on the medial side of the distal tibia

metacarpal bone

one of the five long bones that form the palm of the hand; numbered 1–5, starting on the lateral (thumb) side of the hand

metacarpophalangeal joint

articulation between the distal end of a metacarpal bone of the hand and a proximal phalanx bone of the thumb or a finger

metatarsal bone

one of the five elongated bones that forms the anterior half of the foot; numbered 1–5, starting on the medial side of the foot

metatarsophalangeal joint

articulation between a metatarsal bone of the foot and the proximal phalanx bone of a toe

navicular

tarsal bone that articulates posteriorly with the talus bone, laterally with the cuboid bone, and anteriorly with the medial, intermediate, and lateral cuneiform bones

neck of the femur

narrowed region located inferior to the head of the femur

neck of the radius

narrowed region immediately distal to the head of the radius

obturator foramen

large opening located in the anterior hip bone, between the pubis and ischium regions

olecranon

expanded posterior and superior portions of the proximal ulna; forms the bony tip of the elbow

olecranon fossa

large depression located on the posterior side of the distal humerus; this space receives the olecranon process of the ulna when the elbow is fully extended

patella

kneecap; the largest sesamoid bone of the body; articulates with the distal femur

patellar surface

smooth groove located on the anterior side of the distal femur, between the medial and lateral condyles; site of articulation for the patella

pectineal line

narrow ridge located on the superior surface of the superior pubic ramus

pectoral girdle

shoulder girdle; the set of bones, consisting of the scapula and clavicle, which attaches each upper limb to the axial skeleton

pelvic brim

pelvic inlet; the dividing line between the greater and lesser pelvic regions; formed by the superior margin of the pubic symphysis, the pectineal lines of each pubis, the arcuate lines of each ilium, and the sacral promontory

pelvic girdle

hip girdle; consists of a single hip bone, which attaches a lower limb to the sacrum of the axial skeleton

pelvic inlet

pelvic brim

pelvic outlet

inferior opening of the lesser pelvis; formed by the inferior margin of the pubic symphysis, right and left ischiopubic rami and sacrotuberous ligaments, and the tip of the coccyx

pelvis

ring of bone consisting of the right and left hip bones, the sacrum, and the coccyx

pisiform

from the lateral side, the fourth of the four proximal carpal bones; articulates with the anterior surface of the triquetrum

pollex

(also, thumb) digit 1 of the hand

posterior inferior iliac spine

small, bony projection located at the inferior margin of the auricular surface on the posterior ilium

posterior superior iliac spine

rounded, posterior end of the iliac crest

proximal tibiofibular joint

articulation between the head of the fibula and the inferior aspect of the lateral condyle of the tibia

pubic arch

bony structure formed by the pubic symphysis, and the bodies and inferior pubic rami of the right and left pubic bones

pubic body

enlarged, medial portion of the pubis region of the hip bone

pubic symphysis

joint formed by the articulation between the pubic bodies of the right and left hip bones

pubic tubercle

small bump located on the superior aspect of the pubic body

pubis

anterior portion of the hip bone

radial fossa

small depression located on the anterior humerus above the capitulum; this space receives the head of the radius when the elbow is maximally flexed

radial notch of the ulna

small, smooth area on the lateral side of the proximal ulna; articulates with the head of the radius as part of the proximal radioulnar joint

radial tuberosity

oval-shaped, roughened protuberance located on the medial side of the proximal radius

radiocarpal joint

wrist joint, located between the forearm and hand regions of the upper limb; articulation formed proximally by the distal end of the radius and the fibrocartilaginous pad that unites the distal radius and ulna bone, and distally by the scaphoid, lunate, and triquetrum carpal bones

radius

bone located on the lateral side of the forearm

sacroiliac joint

joint formed by the articulation between the auricular surfaces of the sacrum and ilium

scaphoid

from the lateral side, the first of the four proximal carpal bones; articulates with the radius proximally, the trapezoid, trapezium, and capitate distally, and the lunate medially

scapula

shoulder blade bone located on the posterior side of the shoulder

shaft of the femur

cylindrically shaped region that forms the central portion of the femur

shaft of the fibula

elongated, slender portion located between the expanded ends of the fibula

shaft of the humerus

narrow, elongated, central region of the humerus

shaft of the radius

narrow, elongated, central region of the radius

shaft of the ulna

narrow, elongated, central region of the ulna

sternal end of the clavicle

medial end of the clavicle that articulates with the manubrium of the sternum

sternoclavicular joint

articulation between the manubrium of the sternum and the sternal end of the clavicle; forms the only bony attachment between the pectoral girdle of the upper limb and the axial skeleton

styloid process of the radius

pointed projection located on the lateral end of the distal radius

styloid process of the ulna

short, bony projection located on the medial end of the distal ulna

subpubic angle

inverted V-shape formed by the convergence of the right and left ischiopubic rami; this angle is greater than 80 degrees in females and less than 70 degrees in males

subscapular fossa

broad depression located on the anterior (deep) surface of the scapula

superior angle of the scapula

corner of the scapula between the superior and medial borders of the scapula

superior border of the scapula

superior margin of the scapula

superior pubic ramus

narrow segment of bone that passes laterally from the pubic body to join the ilium

suprascapular notch

small notch located along the superior border of the scapula, medial to the coracoid process

supraspinous fossa

narrow depression located on the posterior scapula, superior to the spine

surgical neck

region of the humerus where the expanded, proximal end joins with the narrower shaft

talus

tarsal bone that articulates superiorly with the tibia and fibula at the ankle joint; also articulates inferiorly with the calcaneus bone and anteriorly with the navicular bone

tarsal bone

one of the seven bones that make up the posterior foot; includes the calcaneus, talus, navicular, cuboid, medial cuneiform, intermediate cuneiform, and lateral cuneiform bones

thigh

portion of the lower limb located between the hip and knee joints

tibia

shin bone; the large, weight-bearing bone located on the medial side of the leg

tibial tuberosity

elevated area on the anterior surface of the proximal tibia

trapezium

from the lateral side, the first of the four distal carpal bones; articulates with the scaphoid proximally, the first and second metacarpals distally, and the trapezoid medially

trapezoid

from the lateral side, the second of the four distal carpal bones; articulates with the scaphoid proximally, the second metacarpal distally, the trapezium laterally, and the capitate medially

triquetrum

from the lateral side, the third of the four proximal carpal bones; articulates with the lunate laterally, the hamate distally, and has a facet for the pisiform

trochlea

pulley-shaped region located medially at the distal end of the humerus; articulates at the elbow with the trochlear notch of the ulna

trochlear notch

large, C-shaped depression located on the anterior side of the proximal ulna; articulates at the elbow with the trochlea of the humerus

ulna

bone located on the medial side of the forearm

ulnar notch of the radius

shallow, smooth area located on the medial side of the distal radius; articulates with the head of the ulna at the distal radioulnar joint