Chapter 9

Gouty Arthritis Uric acid (a substance that gives urine its name)

is a waste product produced during the metabolism of nucleic acid (DNA and RNA) subunits.

Depression (de-PRESH-un = to press down)

is an inferior movement of a part of the body, such as opening the mouth to depress the mandible (Figure 9.9b) or returning shrugged shoulders to the anatomical position to depress the scapula and clavicle.

note

The dense irregular connective tissue is typically arranged as a bundle (ligament), allowing the joint to permit limited movement.

Nerve and Blood Supply

The nerves that supply a joint are the same as those that supply the skeletal muscles that move the joint.

Joints are classified structurally, based on their anatomical characteristics, and functionally, based on the type of movement they permit. The structural classification of joints is based on two criteria:

(1) the presence or absence of a space between the articulating bones, called a synovial cavity, and (2) the type of connective tissue that binds the bones together. Structurally, joints are classified as one of the following types:

In rotation (rō-TĀ-shun; rota- = revolve),

a bone revolves around its own longitudinal axis

A joint without a synovial (joint) cavity where the articulating bones are held tightly together by cartilage, allowing little or no movement.Cartilaginous joints)

There is no synovial cavity, and the bones are held together by cartilage.

Eversion (ē-VER-zhun = to turn outward

) is a movement of the sole laterally at the intertarsal joints (Figure 9.9f). Physical therapists also refer to eversion combined with dorsiflexion of the feet as pronation.

note

Because the synovial cavity allows considerable movement at a joint, all synovial joints are classified functionally as freely movable (diarthroses).

Structure of a typical synovial joint

Note the two layers of the articular capsule—the fibrous membrane and the synovial membrane. Synovial fluid lubricates the synovial cavity, which is located between the synovial membrane and the articular cartilage. The distinguishing feature of a synovial joint is the synovial cavity between the articulating bones.

note

The midline of the body is not used as a point of reference for abduction and adduction of the digits. In abduction of the fingers (but not the thumb), an imaginary line is drawn through the longitudinal axis of the middle (longest) finger, and the fingers move away (spread out) from the middle finger (Figure 9.6d). In abduction of the thumb, the thumb moves away from the palm in the sagittal plane (see Figure 11.18g). Abduction of the toes is relative to an imaginary line drawn through the second toe. Adduction of the fingers and toes returns them to the anatomical position. Adduction of the thumb moves the thumb toward the palm in the sagittal plane (see Figure 11.18g).

Bursae and Tendon Sheaths

The various movements of the body create friction between moving parts.

The bones at a synovial joint are covered by

a layer of hyaline cartilage called articular cartilage. The cartilage covers the articulating surfaces of the bones with a smooth, slippery surface but does not bind them together. Articular cartilage reduces friction between bones in the joint during movement and helps to absorb shock.

Rheumatism

a painful condition involving the joints and muscles is any painful disorder of the supporting structures of the body—bones, ligaments, tendons, or muscles—that is not caused by infection or injury

A tendon sheath protects

all sides of a tendon from friction as the tendon slides back and forth

The articular capsule is composed of two layers

an outer fibrous membrane and an inner synovial membrane

An example of epiphyseal cartilage is the

epiphyseal (growth) plate that connects the epiphysis and diaphysis of a growing bone (Figure 9.2c).

Synovial fluid consists of

hyaluronic acid secreted by synovial cells in the synovial membrane and interstitial fluid filtered from blood plasma.It forms a thin film over the surfaces within the articular capsule.

Functionally, epiphyseal cartilage is an

immovable joint (synarthrosis). When bone elongation ceases, bone replaces the hyaline cartilage, and becomes a synostosis, a bony joint.

Retraction (rē-TRAK-shun = to draw back)

is a movement of a protracted part of the body back to the anatomical position (Figure 9.9d).

Opposition (op-ō-ZISH-un)

is the movement of the thumb at the carpometacarpal joint (between the trapezium and metacarpal of the thumb) in which the thumb moves across the palm to touch the tips of the fingers on the same hand (Figure 9.9i). These "opposable thumbs" allow the distinctive digital movement that gives humans and other primates the ability to grasp and manipulate objects very precisely.

The study of motion of the human body is called

kinesiology (ki-nē-sē-OL-o-jē; kinesi- = movement)

Its functions include

reducing friction by lubricating the joint, absorbing shocks, and supplying oxygen and nutrients to and removing carbon dioxide and metabolic wastes from the chondrocytes within articular cartilage. (Recall that cartilage is an avascular tissue, so it does not have blood vessels to perform the latter function.)

. The spinal cord and brain

respond by sending impulses through different nerves to the muscles to adjust body movements.

Hyperextension of hinge joints

such as the elbow, interphalangeal, and knee joints, is usually prevented by the arrangement of ligaments and the anatomical alignment of the bones.

Some sutures, although present during growth of the skull, are replaced by bone in the adult. Such a suture is called a

synostosis (sin′-os-TŌ-sis; os- = bone), or bony joint—a joint in which there is a complete fusion of two separate bones into one.

A sleevelike articular capsule or joint capsule surrounds a

synovial joint, encloses the synovial cavity, and unites the articulating bones

The fibrous membrane

usually consists of dense irregular connective tissue (mostly collagen fibers) that attaches to the periosteum of the articulating bones

Gliding

is a simple movement in which nearly flat bone surfaces move back-and-forth and from side-to-side with respect to one another (Figure 9.4). There is no significant alteration of the angle between the bones. Gliding movements are limited in range due to the structure of the articular capsule and associated ligaments and bones; however, these sliding movements can also be combined with rotation. The intercarpal and intertarsal joints are examples of articulations where gliding movements occur.

The outer layer, known as the parietal layer

is attached to bone (see Figure 11.18a). Between the layers is a cavity that contains a film of synovial fluid

extension is simply the reverse of these movements):

1 Bending the head toward the chest at the atlanto-occipital joints between the atlas (the first vertebra) and the occipital bone of the skull, and at the cervical intervertebral joints between the cervical vertebrae (Figure 9.5a) 2Bending the trunk forward at the intervertebral joints as in doing a crunch with your abdominal muscles 3Moving the humerus forward at the shoulder joint, as in swinging the arms forward while walking (Figure 9.5b)

Extracapsular ligaments lie outside the articular capsule

Examples are the fibular and tibial collateral ligaments of the knee joint. Intracapsular ligaments occur within the articular capsule but are excluded from the synovial cavity by folds of the synovial membrane. Examples are the anterior and posterior cruciate ligaments of the knee joint.

Joint Classifications

by type of ligaments ; presence of joint cavity; stucture; type of movement they allow

Pronation (prō-NĀ-shun)

is a movement of the forearm at the proximal and distal radioulnar joints in which the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly (Figure 9.9h).

The strength of these fiber bundles, called ligaments (liga- = bound or tied)

is one of the principal mechanical factors that hold bones close together in a synovial joint. Ligaments are often designated by individual names

A dislocation (dis′-lō-KĀ-shun; dis- = apart) or luxation (luks-Ā-shun; luxatio = dislocation)

is the displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsules

Abduction (ab- = away; -duct- = to lead) or radial deviation is the.

movement of a bone away from the midline body

adduction (ad-DUK-shun; ad- = toward) or ulnar deviation is the

movement of a bone toward the midline. Both movements usually occur along the frontal plane.

note

We are all familiar with the cracking sounds heard as certain joints move, or the popping sounds that arise when a person pulls on his fingers to crack his knuckles. According to one theory, when the synovial cavity expands, the pressure inside the synovial cavity decreases, creating a partial vacuum. The suction draws carbon dioxide and oxygen out of blood vessels in the synovial membrane, forming bubbles in the fluid. When the fingers are flexed (bent) the volume of the cavity decreases and the pressure increases; this bursts the bubbles and creates cracking or popping sounds as the gases are driven back into solution.

In fact, the fibrous membrane is literally

a thickened continuation of the periosteum between the bones

In a saddle joint or sellar joint (SEL-ar), the articular surface of one bone is saddle-shaped,

and the articular surface of the other bone fits into the "saddle" as a sitting rider would sit (Figure 9.10e). The movements at a saddle joint are the same as those at a condyloid joint: biaxial (flexion-extension and abduction-adduction) plus limited circumduction.

Examples of circumduction

are moving the humerus in a circle at the shoulder joint (Figure 9.7a), moving the hand in a circle at the wrist joint, moving the thumb in a circle at the carpometacarpal joint, moving the fingers in a circle at the metacarpophalangeal joints (between the metacarpals and phalanges), and moving the femur in a circle at the hip joint (Figure 9.7b). Both the shoulder and hip joints permit circumduction. Flexion, abduction, extension, and adduction are more limited in the hip joints than in the shoulder joints due to the tension on certain ligaments and muscles and the depth of the acetabulum in the hip joint (see Sections 9.10 and 9.12).

A condyloid joint is

biaxial because the movement it permits is around two axes (flexion-extension and abduction-adduction), plus limited circumduction (remember that circumduction is not an isolated movement). Examples of condyloid joints are the radiocarpal (wrist) and metacarpophalangeal joints (between the metacarpals and proximal phalanges) of the second through fifth digits.

Saclike structures called

bursae (A sac or pouch of synovial fluid located at friction points, especially about joints.) are strategically situated to alleviate friction in some joints, such as the shoulder and knee joints (see Figures 9.12 and 9.15c).

An example is the

coronal suture between the parietal and frontal bones

In gouty arthritis,

inflammation and painful swelling of joints caused by excessive uric acid in the body, sodium urate crystals are deposited in the soft tissues of the joints.

RA is characterized by

inflammation of the joint, which causes swelling, pain, and loss of function. Usually, this form of arthritis occurs bilaterally: If one wrist is affected, the other is also likely to be affected, although they are often not affected to the same degree.

Tenosynovitis of the

inflammation of the tendon and synovial membrane dorsum of the foot may be caused by tying shoelaces too tightly. Gymnasts are prone to developing the condition as a result of chronic, repetitive, and maximum hyperextension at the wrists. Other repetitive movements involving activities such as typing, haircutting, carpentry, and assembly line work can also result in tenosynovitis.

Some examples of plane joints are the

intercarpal joints (between carpal bones at the wrist), intertarsal joints (between tarsal bones at the ankle), sternoclavicular joints (between the manubrium of the sternum and the clavicle), acromioclavicular joints (between the acromion of the scapula and the clavicle), sternocostal joints (between the sternum and ends of the costal cartilages at the tips of the second through seventh pairs of ribs), and vertebrocostal joints (between the heads and tubercles of ribs and bodies and transverse processes of thoracic vertebrae).

•Plantar flexion (PLAN-tar

involves bending of the foot at the ankle joint in the direction of the plantar or inferior surface (see Figure 9.9g), as when you elevate your body by standing on your toes.

•Protraction (prō-TRAK-shun = to draw forth)

is a movement of a part of the body anteriorly in the transverse plane. Its opposing movement is retraction. You can protract your mandible at the temporomandibular joint by thrusting it outward (Figure 9.9c) or protract your clavicles at the acromioclavicular and sternoclavicular joints by crossing your arms.

version (ē-VER-zhun = to turn outward

is a movement of the sole laterally at the intertarsal joints (Figure 9.9f). Physical therapists also refer to eversion combined with dorsiflexion of the feet as pronation.

Elevation (el-e-VĀ-shun = to lift up)

is a superior movement of a part of the body, such as closing the mouth at the temporomandibular joint (between the mandible and temporal bone) to elevate the mandible (Figure 9.9a) or shrugging the shoulders at the acromioclavicular joint to elevate the scapula and clavicle. Its opposing movement is depression. Other bones that may be elevated (or depressed) include the hyoid and ribs.

Rheumatoid arthritis (RA)

is an autoimmune disease in which the immune system of the body attacks its own tissues—in this case, its own cartilage and joint linings

Circumduction (ser-kum-DUK-shun; circ- = circle

is movement of the distal end of a body part in a circle (Figure 9.7). Circumduction is not an isolated movement by itself but rather a continuous sequence of flexion, abduction, extension, adduction, and rotation of the joint (or in the opposite order). It does not occur along a separate axis or plane of movement

Fibrous Joints

lack a synovial cavity, and the articulating bones are held very closely together by dense irregular connective tissue. Fibrous joints permit little or no movement. The three types of fibrous joints are sutures, syndesmoses, and interosseous membranes.

This movement, which occurs along the frontal plane and involves the intervertebral joints, is called

lateral flexion

The functions of the menisci are

not completely understood but are known to include the following: (1) shock absorption; (2) a better fit between articulating bony surfaces; (3) providing adaptable surfaces for combined movements; (4) weight distribution over a greater contact surface; and (5) distribution of synovial lubricant across the articular surfaces of the joint.

Examples

of abduction include moving the humerus laterally at the shoulder joint, moving the palm laterally at the wrist joint, and moving the femur laterally at the hip joint (Figure 9.6a-c). The movement that returns each of these body parts to the anatomical position is adduction (Figure 9.6a-c).

Elevation

of the injured area above the level of the heart, when possible, will reduce potential swelling

Two major distinctions between osteoarthritis and rheumatoid arthritis are that

osteoarthritis first afflicts the larger joints (knees, hips) and is due to wear and tear, whereas rheumatoid arthritis first strikes smaller joints and is an active attack on the cartilage. Osteoarthritis is the most common reason for hip- and knee-replacement surgery.

A "double-jointed

person does not really have extra joints. Individuals who are double-jointed have greater flexibility in their articular capsules and ligaments; the resulting increase in range of motion allows them to entertain fellow partygoers with activities such as touching their thumbs to their wrists and putting their ankles or elbows behind their necks. Unfortunately, such flexible joints are less structurally stable and are more easily dislocated.

Synovial fluid also contains

phagocytic cells that remove microbes and the debris that results from normal wear and tear in the joint

Osteoarthritis is a

progressive disorder of synovial joints, particularly weight-bearing joints. Articular cartilage deteriorates and new bone forms in the subchondral areas and at the margins of the joint

Initially sprains should be treated with PRICE:

protection, rest, ice, compression, and elevation. PRICE therapy may be used on muscle strains, joint inflammation, suspected fractures, and bruises.

orsiflexion (dor-si-FLEK-shun)

refers to bending of the foot at the ankle or talocrural joint (between the tibia, fibula, and talus) in the direction of the dorsum (superior surface) (Figure 9.9g). Dorsiflexion occurs when you stand on your heels. Its opposing movement is plantar flexion.

In a pivot joint, or trochoid joint (TRŌ-koyd), the

rounded or pointed surface of one bone articulates with a ring formed partly by another bone and partly by a ligament (Figure 9.10c). A pivot joint is uniaxial because it allows rotation only around its own longitudinal axis.

examples of pivot joints are

the atlanto-axial joint, in which the atlas rotates around the axis and permits the head to turn from side-to-side as when you shake your head "no" (see Figure 9.8a), and the radioulnar joints that enable the palms to turn anteriorly and posteriorly as the head of the radius pivots around its long axis in the radial notch of the ulna (see Figure 9.9h).

When a synovial joint is immobile for a time

the fluid becomes quite viscous (gel-like), but as joint movement increases, the fluid becomes less viscous.

For example

the frontal bone grows in halves that join together across a suture line. Usually they are completely fused by age 6 and the suture becomes obscure. If the suture persists beyond age 6, it is called a frontal (metopic) suture (me-TŌ-pik; metopon = forehead). A synostosis is classified as a synarthrosis because it is immovable.

Both movements usually occur along

the sagittal plane. All of the following are examples of flexion (as you have probably already guessed,

The irregular, interlocking edges of sutures give

them added strength and decrease their chance of fracturing. Sutures are joints that form as the numerous bones of the skull come in contact during development.They are immovable or slightly movable. In older individuals, sutures are immovable (synarthroses), but in infants and children they are slightly movable (amphiarthroses) (Figure 9.1b). Sutures play important roles in shock absorption in the skull.

Structures called tendon sheaths also reduce friction at joints. Tendon sheaths or synovial sheaths are tubelike bursae;

they wrap around certain tendons that experience considerable friction as they pass through tunnels formed by connective tissue and bone. The inner layer of a tendon sheath, the visceral layer, is attached to the surface of the tendon

Tendon sheaths are found

where tendons pass through synovial cavities, such as the tendon of the biceps brachii muscle at the shoulder joint (see Figure 9.12c)

The final category of fibrous joint is the interosseous membrane

which is a substantial sheet of dense irregular connective tissue that binds neighboring long bones and permits slight movement (amphiarthrosis).

The functional classification of joints relates to the degree of movement they permit. Functionally, joints are classified as one of the following types: Synarthrosis (am′-fē-ar-THRŌ-sis; amphi- = on both sides) (An immovable joint such as a suture, gomphosis, or synchondrosis.)

A slightly movable joint. The plural is amphiarthroses.

A sprain

An injury in which the ligaments holding bones together are stretched too far and tear. is the forcible wrenching or twisting of a joint that stretches or tears its ligaments but does not dislocate the bones. It occurs when the ligaments are stressed beyond their normal capacity. Severe sprains may be so painful that the joint cannot be moved. There is considerable swelling, which results from chemicals released by the damaged cells and hemorrhage of ruptured blood vessels. The lateral ankle joint is most often sprained; the wrist is another area that is frequently sprained.

Although flexion and extension usually occur along the sagittal plane, there are a few exceptions

For example, flexion of the thumb involves movement of the thumb medially across the palm at the carpometacarpal joint between the trapezium and metacarpal of the thumb, as when you touch your thumb to the opposite side of your palm (see Figure 11.18g). Another example is movement of the trunk sideways to the right or left at the waist.

There are two principal interosseous membrane joints in the human body

One occurs between the radius and ulna in the forearm (see Figure 8.5) and the other occurs between the tibia and fibula in the leg (Figure 9.1d)

note

The dense irregular connective tissue between a tooth and its socket is the thin periodontal ligament (membrane). A healthy gomphosis permits minute shock-absorbing movements (amphiarthrosis). Inflammation and degeneration of the gums, periodontal ligament, and bone is called periodontal disease.

Joints and Homeostasis

The joints of the skeletal system contribute to homeostasis by holding bones together in ways that allow for movement and flexibility.

Fibrous joints(A joint that allows little or no movement, such as a suture, syndesmosis or interosseous membrane.)

There is no synovial cavity, and the bones are held together by dense irregular connective tissue that is rich in collagen fibers.

note:

These strong connective tissue sheets not only help hold these adjacent long bones together, they also play an important role in defining the range of motion between the neighboring bones and provide an increased attachment surface for muscles that produce movements of the digits of the hand and foot.

Movements at synovial joints are grouped into four main categories:

(1) gliding, (2) angular movements, (3) rotation, and (4) special movements, which occur only at certain joints.

Epiphyseal cartilages

are actually hyaline cartilage growth centers during endochondral bone formation, not joints associated with movements.

The scientific study of joints is termed

arthrology

Veins remove

carbon dioxide and wastes from the joints.

An example of a saddle joint is the

carpometacarpal joint between the trapezium of the carpus and metacarpal of the thumb.

The flexibility of the fibrous membrane permits

considerable movement at a joint, while its great tensile strength (resistance to stretching) helps prevent the bones from dislocating, the displacement of a bone from a joint. The fibers of some fibrous membranes are arranged as parallel bundles of dense regular connective tissue that are highly adapted for resisting strains.

In a hinge joint, or ginglymus joint (JIN-gli-mus), the

convex surface of one bone fits into the concave surface of another bone (Figure 9.10b).

extension is simply the reverse of these movements):

4Moving the forearm toward the arm at the elbow joint between the humerus, ulna, and radius as in bending your elbow (Figure 9.5c) 5Moving the palm toward the forearm at the wrist or radiocarpal joint between the radius and carpals, as in the upward movement when doing wrist curls (Figure 9.5d) 6Bending the digits of the hand at the interphalangeal joints between phalanges as in clenching your fingers to make a fist 7Moving the femur forward at the hip joint between the femur and hip bone, as in walking (Figure 9.5e) 8Moving the heel toward the buttock at the tibiofemoral joint between the tibia, femur, and patella, as occurs when bending the knee (Figure 9.5f)

Diarthrosis (dī-ar-THRŌ-sis = movable joint)

A freely movable joint. The plural is diarthroses. All diarthroses are synovial joints. They have a variety of shapes and permit several different types of movements.

Types of Synovial Joints

Although all synovial joints have many characteristics in common, the shapes of the articulating surfaces vary; thus, many types of movements are possible. Synovial joints are divided into six categories based on type of movement: plane, hinge, pivot, condyloid, saddle, and ball-and-socket.

Flexion, Extension, Lateral Flexion, and Hyperextension

Flexion and extension are opposite movements.

the head from side to side at the atlanto-axial joint (between the atlas and axis), as when you shake your head "no" (Figure 9.8a). Another is turning the trunk from side-to-side at the intervertebral joints while keeping the hips and lower limbs in the anatomical position. In the limbs, rotation is defined relative to the midline, and specific qualifying terms are used. If the anterior surface of a bone of the limb is turned toward the midline, the movement is called medial (internal) rotation.

One example is turning

You can medially rotate the humerus at the shoulder joint as follows:

Starting in the anatomical position, flex your elbow and then move your palm across the chest (Figure 9.8b). You can medially rotate the femur at the hip joint as follows: Lie on your back, bend your knee, and then move your leg and foot laterally from the midline. Although you are moving your leg and foot laterally, the femur is rotating medially (Figure 9.8c). Medial rotation of the leg at the knee joint can be produced by sitting on a chair, bending your knee, raising your lower limb off the floor, and turning your toes medially. If the anterior surface of the bone of a limb is turned away from the midline, the movement is called lateral (external) rotation (see Figure 9.8b, c).

note

The arterial branches from several different arteries typically merge around a joint before penetrating the articular capsule. The chondrocytes in the articular cartilage of a synovial joint receive oxygen and nutrients from synovial fluid derived from blood; all other joint tissues are supplied directly by capillaries. Carbon dioxide and wastes pass from chondrocytes of articular cartilage into synovial fluid and then into veins; carbon dioxide and wastes from all other joint structures pass directly into veins.

A spiral-shaped bacterium called Borrelia burgdorferi causes Lyme disease, named for the town of Lyme, Connecticut, where it was first reported in 1975.

The bacteria are transmitted to humans mainly by deer ticks (Ixodes dammini). These ticks are so small that their bites often go unnoticed. Within a few weeks of the tick bite, a rash may appear at the site. Although the rash often resembles a bull's-eye target, there are many variations, and some people never develop a rash. Other symptoms include joint stiffness, fever and chills, headache, stiff neck, nausea, and low back pain. In advanced stages of the disease, arthritis is the main complication. It usually afflicts the larger joints such as the knee, ankle, hip, elbow, or wrist. Antibiotics are generally effective against Lyme disease, especially if they are given promptly. However, some symptoms may linger for years.

Synovial joints(sin′-ar-THRŌ-sis; syn- = together) (A fully movable or diarthrotic joint in which a synovial (joint) cavity is present between the two articulating bones.)

The bones forming the joint have a synovial cavity and are united by the dense irregular connective tissue of an articular capsule, and often by accessory ligaments.

note

The pubic symphysis between the anterior surfaces of the hip bones is one example of a symphysis (Figure 9.2b). This type of joint is also found at the junction of the manubrium and body of the sternum (see Figure 7.22) and at the intervertebral joints between the bodies of vertebrae (see Figure 7.20a). A portion of the intervertebral disc is composed of fibrocartilage. A symphysis is a slightly movable joint (amphiarthrosis).

The synovial membrane secretes synovial fluid (ov- = egg)synovial membrane is also Secretion of synovial membranes that lubricates joints and nourishes articular cartilage.

a viscous, clear or pale yellow fluid named for its similarity in appearance and consistency to uncooked egg white

The articulating surfaces of bones in a plane joint (PLĀN), also called a planar joint

are flat or slightly curved

Although many of the components of synovial joints are avascular,

arteries in the vicinity send out numerous branches that penetrate the ligaments and articular capsule to deliver oxygen and nutrients.

osteoarthritis affects mainly the

articular cartilage, although the synovial membrane often becomes inflamed late in the disease.

The only examples of gomphoses in the human body are the

articulations between the roots of the teeth (cone-shaped pegs) and their sockets (dental alveoli) in the alveolar processes in the maxillae and mandible (Figure 9.1c, right).

Tendon sheaths are also found

at the wrist and ankle, where many tendons come together in a confined space (see Figure 11.18a), and in the fingers and toes, where there is a great deal of movement (see Figure 11.18).

Plane joints primarily permit

back-and-forth and side-to-side movements between the flat surfaces of bones, but they may also rotate against one another. Many plane joints are biaxial, meaning that they permit movement in two axes.

A ball-and-socket joint or spheroid joint (SFĒ-royd) consists of the

ball-like surface of one bone fitting into a cuplike depression of another bone (Figure 9.10f). Such joints are triaxial (multiaxial), permitting movements around three axes (flexion-extension, abduction-adduction, and rotation)

Compression

by wrap or bandage helps to reduce swelling. Care must be taken to compress the injured area but not to block blood flow.

Inside some synovial joints, such as the knee, crescent-shaped pads of fibrocartilage lie between the articular surfaces of the bones and are attached to the fibrous capsule. These pads are

called articular discs or menisci (me-NIS-sī or me-NIS-kī; singular is meniscus). Figures 9.15c and d depict the lateral and medial menisci in the knee joint. The discs bind strongly to the inside of the fibrous membrane and usually subdivide the synovial cavity into two spaces, allowing separate movements to occur in each space. As you will see later, separate movements also occur in the respective compartments of the temporomandibular joint (TMJ) (see Section

A dislocated mandible

displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsules can occur in several ways. Anterior displacements are the most common and occur when the condylar processes of the mandible pass anterior to the articular tubercles. Common causes are extreme mouth opening, as in yawning or taking a large bite, dental procedures, or general anesthesia. Posterior displacement can be caused by a direct blow to the chin. Superior displacements are typically caused by a direct blow to a partially opened mouth. Lateral dislocations are usually associated with mandibular fractures.

Many synovial joints also contain accessory ligaments called

extracapsular ligaments and intracapsular ligaments

Synovial joints

freely movable joints,have certain characteristics that distinguish them from other joints

Another example of a syndesmosis is called a

gomphosis (gom-FŌ-sis; gompbo- = bolt or nail) or dentoalveolar joint, in which a cone-shaped peg fits into a socket

Arthritis

inflammation of a joint is a form of rheumatism in which the joints are swollen, stiff, and painful. It afflicts about 45 million people in the United States and is the leading cause of physical disability among adults over age 65.

A synchondrosis (sin′-kon-DRŌ-sis; chondro- = cartilage; plural is synchondroses) A cartilaginous joint in which the connecting material is hyaline cartilage.

is a cartilaginous joint in which the connecting material is hyaline cartilage and is slightly movable (amphiarthrosis) to immovable (synarthrosis). One example of a synchondrosis is the joint between the first rib and the manubrium of the sternum (Figure 9.2a).

A symphysis (SIM-fi-sis = growing together; plural is symphyses)

is a cartilaginous joint in which the ends of the articulating bones are covered with hyaline cartilage, but a broad, flat disc of fibrocartilage connects the bones

Osteoarthritis (OA)

is a degenerative joint disease in which joint cartilage is gradually lost. It results from a combination of aging, obesity, irritation of the joints, muscle weakness, and wear and abrasion. Commonly known as "wear-and-tear" arthritis, osteoarthritis is the most common type of arthritis.

A suture (SOO-chur; sutur = seam)An immovable fibrous joint that joins skull bones.

is a fibrous joint composed of a thin layer of dense irregular connective tissue; sutures occur only between bones of the skull

A syndesmosis (sin′-dez-MŌ-sis; syndesmo- = band or ligament; plural is syndesmoses), also is A slightly movable joint in which articulating bones are united by fibrous connective tissue.

is a fibrous joint in which there is a greater distance between the articulating surfaces and more dense irregular connective tissue than in a suture

Supination (soo-pi-NĀ-shun)

is a movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly (Figure 9.9h). This position of the palms is one of the defining features of the anatomical position. Its opposing movement is pronation.

A joint is A point of contact between two bones, between bone and cartilage, or between bone and teeth. Also called an articulation or arthrosis.also called an articulation is a point of contact between bones, cartilage and bones, or teeth and bones.or arthrosis is a joint or articulation

is a point of contact between two bones, between bone and cartilage, or between bone and teeth

A strain

is a stretched or partially torn muscle or muscle and tendon. It often occurs when a muscle contracts suddenly and powerfully—such as the leg muscles of sprinters when they spring from the blocks.

Tenosynovitis (ten′-o-sīn-ō-VĪ-tis)

is an inflammation of the tendons, tendon sheaths, and synovial membranes surrounding certain joints. The tendons most often affected are at the wrists, shoulders, elbows (resulting in tennis elbow), finger joints (resulting in trigger finger), ankles, and feet. The affected sheaths sometimes become visibly swollen because of fluid accumulation. Tenderness and pain are frequently associated with movement of the body part. The condition often follows trauma, strain, or excessive exercise.

The inner layer of the articular capsule, the synovial membrane is also the deeper of the two layers of the articular capsule of a synovial joint, composed of areolar connective tissue that secretes synovial fluid into the synovial (joint) cavity.

is composed of areolar connective tissue with elastic fibers. At many synovial joints the synovial membrane includes accumulations of adipose tissue, called articular fat pads. An example is the infrapatellar fat pad in the knee (see Figure 9.15c).

The primary symptom of RA is

is inflammation of the synovial membrane. If untreated, the membrane thickens, and synovial fluid accumulates. The resulting pressure causes pain and tenderness. The membrane then produces an abnormal granulation tissue, called pannus, that adheres to the surface of the articular cartilage and sometimes erodes the cartilage completely. When the cartilage is destroyed, fibrous tissue joins the exposed bone ends. The fibrous tissue ossifies and fuses the joint so that it becomes immovable—the ultimate crippling effect of RA. Growth of the granulation tissue causes the distortion of the fingers that characterizes hands of RA sufferers.

Inversion (in-VER-zhun = to turn inward)

is movement of the sole medially at the intertarsal joints (between the tarsals) (Figure 9.9e). Its opposing movement is eversion. Physical therapists also refer to inversion combined with plantar flexion of the feet as supination.

One example of a syndesmosis

is the distal tibiofibular joint, where the anterior tibiofibular ligament connects the tibia and fibula (Figure 9.1c, left)It permits slight movement (amphiarthrosis)

Like a fibrous joint, a cartilaginous joint

lacks a synovial cavity and allows little or no movement. Here the articulating bones are tightly connected by either hyaline cartilage or fibrocartilage (see Table 4.6). The three types of cartilaginous joints are synchondroses, symphyses, and epiphyseal cartilages.

Bursae can be

located between the skin and bones, tendons and bones, muscles and bones, or ligaments and bones. The fluid-filled bursal sacs cushion the movement of these body parts against one another.

Synovial joints contain

many nerve endings that are distributed to the articular capsule and associated ligaments. Some of the nerve endings convey information about pain from the joint to the spinal cord and brain for processing Other nerve endings respond to the degree of movement and stretch at a joint, such as when a physician strikes the tendon below your kneecap to test your reflexes.

The five components of PRICE therapy are •Protection

means protecting the injury from further damage; for example, stop the activity and use padding and protection, and use splints or a sling, or crutches, if necessary.

All symphyses occur in the

midline of the body

Special movements

occur only at certain joints. They include elevation, depression, protraction, retraction, inversion, eversion, dorsiflexion, plantar flexion, supination, pronation, and opposition (Figure 9.9):

Treatment consists of

pain relief (ibuprofen, naproxen, colchicine, and cortisone) followed by administration of allopurinol to keep uric acid levels low so that crystals do not form.

The unique characteristic of a synovial joint is the

presence of a space called a synovial cavity or joint cavity between the articulating bones. synovial cavity is the space between the articulating bones of a synovial joint, filled with synovial fluid.

As the name implies, hinge joints

produce an angular, opening-and-closing motion like that of a hinged door. In most joint movements, one bone remains in a fixed position while the other moves around an axis Hinge joints are uniaxial (monaxial) because they typically allow motion around a single axis Hinge joints permit only flexion and extension Examples of hinge joints are the knee (actually a modified hinge joint, which will be described later), elbow, ankle, and interphalangeal joints (between the phalanges of the fingers and toes).

A person who suffers from gout (GOWT) either

produces excessive amounts of uric acid or is not able to excrete as much as normal. The result is a buildup of uric acid in the blood. This excess acid then reacts with sodium to form a salt called sodium urate. Crystals of this salt accumulate in soft tissues such as the kidneys and in the cartilage of the ears and joints.

A labrum (LĀ-brum; plural is labra)

prominent in the ball-and-socket joints of the shoulder and hip (see Figures 9.12c, d; 9.14c), is the fibrocartilaginous lip that extends from the edge of the joint socket. The labrum helps deepen the joint socket and increases the area of contact between the socket and the ball-like surface of the head of the humerus or femur.

Examples of ball-and-socket joints are the

shoulder and hip joints. At the shoulder joint, the head of the humerus fits into the glenoid cavity of the scapula. At the hip joint, the head of the femur fits into the acetabulum of the hip (coxal) bone. Table 9.2 summarizes the structural and functional categories of joints.

One of the benefits of warming up before exercise is that it

stimulates the production and secretion of synovial fluid; within limits, more fluid means less stress on the joints during exercise.

An axis is a

straight line around which a bone rotates (revolves) or slides If plane joints rotate in addition to sliding, then they are triaxial (multiaxial), permitting movement in three axes.

Bursae are not

strictly part of synovial joints, but they do resemble joint capsules because their walls consist of an outer fibrous membrane of thin, dense connective tissue lined by a synovial membrane. They are filled with a small amount of fluid that is similar to synovial fluid.

In a condyloid joint (KON-di-loyd; condyl- = knuckle) or ellipsoidal joint,

the convex oval-shaped projection of one bone fits into the oval-shaped depression of another bone (Figure 9.10d).

Ice

the injured area as soon as possible. Applying ice slows blood flow to the area, reduces swelling, and relieves pain. Ice works effectively when applied for 20 minutes, off for 40 minutes, back on for 20 minutes, and so on.

Rest

the injured area to avoid further damage to the tissues. Stop the activity immediately. Avoid exercise or other activities that cause pain or swelling to the injured area. Rest is needed for repair. Exercising before an injury has healed may increase the probability of re-injury.

Gout most often affects

the joints of the feet, especially at the base of the big toe. The crystals irritate and erode the cartilage, causing inflammation, swelling, and acute pain. Eventually, the crystals destroy all joint tissues. If the disorder is untreated, the ends of the articulating bones fuse, and the joint becomes immovable.

In flexion (FLEK-shun; flex- = to bend)

there is a decrease in the angle between articulating bones

in extension (eks-TEN-shun; exten- = to stretch out)

there is an increase in the angle between articulating bones, often to restore a part of the body to the anatomical position after it has been flexed (Figure 9.5)

In angular movements,

there is an increase or a decrease in the angle between articulating bones. The major angular movements are flexion, extension, lateral flexion, hyperextension, abduction, adduction, and circumduction. These movements are discussed with respect to the body in the anatomical position (see Figure 1.5).

Another is turning the

trunk from side-to-side at the intervertebral joints while keeping the hips and lower limbs in the anatomical position. In the limbs, rotation is defined relative to the midline, and specific qualifying terms are used. If the anterior surface of a bone of the limb is turned toward the midline, the movement is called medial (internal) rotation

Continuation of extension beyond the anatomical position is called hyperextension (hī-per-ek-STEN-shun; hyper- = beyond or excessive). Examples of hyperextension include:

•Bending the head backward at the atlanto-occipital and cervical intervertebral joints as in looking up at stars (Figure 9.5a) •Bending the trunk backward at the intervertebral joints as in a backbend •Moving the humerus backward at the shoulder joint, as in swinging the arms backward while walking (Figure 9.5b) •Moving the palm backward at the wrist joint as in preparing to shoot a basketball (Figure 9.5d) •Moving the femur backward at the hip joint, as in walking (Figure 9.5e