Chapter 9 - Joints

What is the knee joint?

(tibiofemoral joint) is the largest and most com- plex joint of the body (Figure 9.15). It is a modified hinge joint (because its primary movement is a uniaxial hinge movement) that consists of three joints within a single synovial cavity

What is a syndesmosis?

-a fibrous joint in which there is a greater distance between the articulating surfaces and more dense irregular connective tissue than in a suture. -The dense irregular connective tissue is typically arranged as a bundle (ligament), al- lowing the joint to permit limited movement.

What are the three joints of the knee joints?

1. Laterally is a tibiofemoral joint, between the lateral condyle of the femur, lateral meniscus, and lateral condyle of the tibia, which is the weight-bearing bone of the leg. 2. Medially is another tibiofemoral joint, between the medial condyle of the femur, medial meniscus, and medial condyle of the tibia. 3. An intermediate patellofemoral joint is between the patella and the patellar surface of the femur.

What is a diarthrosis?

A freely mov- able joint. The plural is diarthroses. All diarthroses are syno- vial joints. They have a variety of shapes and permit several different types of movements.

What are articulations?

A joint, also called an articulation (ar-tik-uˉ-LAˉ-shun) or arthrosis (ar-THRO ̄-sis), is a point of contact between two bones, between bone and cartilage, or between bone and teeth.

What is the labrum of the synovial joints?

A labrum (LAˉ-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.

What is the articular capsule of the synovial joint?

A sleevelike articular capsule or joint capsule surrounds a synovial joint, encloses the synovial cavity, and unites the articulating bones.

What is an amphiarthrosis?

A slightly movable joint. The plural is amphiarthroses

What is an abduction?

Abduction (ab-DUK-shun; ab- away; -duct- to lead) or radial deviation is the movement of a bone away from the midline; 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

What is a lateral flexion?

Another example is move- ment of the trunk sideways to the right or left at the waist. This movement, which occurs along the frontal plane and involves the intervertebral joints, is called lateral flexion

What is a saddle?

Articular surface of one bone is saddle-shaped; articular surface of other bone "sits" in saddle. -biaxial - flexion-extension, abduction-adduction. -Carpometacarpal joint between trapezium and metacarpal of thumb.

What is plane joint?

Articulated surfaces flat or slightly curved. -Many biaxial diarthroses (freely movable): back-and-forth and side- to-side movements. Some triaxial diarthroses: back-and-forth, side-to- side, rotation. -Intercarpal, intertarsal, sternocostal (between sternum and second to seventh pairs of ribs), and vertebrocostal joints.

What are articular fat pads of the synovial membrane of the articular capsule?

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

What is bell and socket?

Ball-like surface fits into cuplike depression. -Triaxial diarthrosis: flexion-extension, abduction-adduction, rotation -shoulder and hip joints

What is the tibial collateral ligament?

Broad, flat ligament on the medial surface of the joint that extends from the medial condyle of the femur to the medial condyle of the tibia

What is circumduction?

Circumduction (ser-kum-DUK-shun; circ- circle) is move- ment of the distal end of a body part in a circle (Figure 9.7). Cir- cumduction is not an isolated movement by itself but rather a con- tinuous sequence of flexion, abduction, extension, adduction, and rotation of the joint (

What is the patellar ligament?

Continuation of common tendon of inser- tion of quadriceps femoris muscle that extends from the pa- tella to the tibial tuberosity. Also strengthens the anterior sur- face of the joint. Posterior surface of the ligament is separated from the synovial membrane of the joint by an infrapatellar fat pad

What is a hyperextension?

Continuation of extension beyond the anatomical position is called hyperextension

What are hinge joints?What are hinge joints?

Convex surface fits into concave surface. -Uniaxial diarthrosis: flexion-extension. -Knee (modified hinge), elbow, ankle, and interphalangeal joints.

What is depression?

Depression (de-PRESH-un to press down) is an inferior move- ment 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.

What is elevation?

Elevation (el-e-VAˉ -shun to lift up) is a superior movement of a part of the body, such as closing the mouth at the temporo- mandibular 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.

What is the posterior cruciate ligament (PCL)?

Extends anteriorly and medially from a depression on the posterior intercondylar area of the tibia and lateral meniscus to the anterior part of the lateral surface of the medial condyle of the femur (Figure 9.15a, b, h). The PCL prevents the posterior sliding of the tibia (and anterior sliding of the femur) when the knee is flexed. This is very important when walking down stairs or a steep incline.

What are the medial and lateral menisci?

Fused tendons of insertion of the quadriceps femoris muscle and the fascia lata (fascia of thigh) that strengthen the anterior surface of the joint

What is gliding?

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

What is medial (internal) rotation?

If the anterior surface of a bone of the limb is turned toward the midline, the movement is called medial (inter- nal) rotation.

What is lateral (external) rotation?

If the anterior surface of the bone of a limb is turned away from the midline, the movement is called lat- eral (external) rotation

What is a frontal or metopic suture?

If the suture persists beyond age 6

What is angular?

In angular movements, there is an increase or a decrease in the angle between articulating bones.

What is flexion?

In flexion (FLEK- shun; flex- to bend) there is a decrease in the angle between articulating bones (ex: Bending the trunk forward at the intervertebral joints as in do- ing a crunch with your abdominal muscles)

What are articular discs (menisci) of the synovial joints?

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. -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 adapt- able surfaces for combined movements; (4) weight distribution over a greater contact surface; and (5) distribution of synovial lu- bricant across the articular surfaces of the joint.

What are the intracapsular accessory ligaments?

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 cru- ciate ligaments of the knee joint

lateral meniscus

Nearly circular piece of fibrocartilage (approaches an incomplete O in shape) (Figure 9.15a, b, d, h). Its anterior end is attached anteriorly to the intercondylar eminence of the tibia, and laterally and posteriorly to the anterior cruciate ligament. Its posterior end is attached posteriorly to the intercondylar eminence of the tibia, and anteriorly to the posterior end of the medial meniscus. The anterior surfaces of the medial and lateral menisci are con- nected to each other by the transverse ligament of the knee (Figure 9.15a) and to the margins of the head of the tibia by the coronary ligaments

What is the articular capsule?

No complete, independent capsule unites the bones of the knee joint. The ligamentous sheath surrounding the joint consists mostly of muscle tendons or their expansions (Figure 9.15e-g). There are, however, some capsular fibers con- necting the articulating bones.

What is opposition?

Opposition (op-oˉ-ZISH-un) is the movement of the thumb at the carpometacarpal joint (between the trapezium and meta- carpal of the thumb) in which the thumb moves across the palm to touch the tips of the fingers on the same hand

What is the fibrous membrane of the articular capsule of the synovial joint?

Outer layer; the fibrous membrane usually consists of dense irregular connective tissue (mostly collagen fibers) that attaches to the periosteum of the articulating bones. -The flexibility of the fibrous membrane permits considerable move- ment at a joint, while its great tensile strength (resistance to stretching) helps prevent the bones from dislocating, the displace- ment of a bone from a joint.

What is a condyloid joint?

Oval-shaped projection fits into oval- shaped depression. -Biaxial diarthrosis: flexion-extension, abduction-adduction. -Radiocarpal and metacarpophalangeal joints.

What is protraction?

Protraction (proˉ-TRAK-shun to draw forth) is a movement of a part of the body anteriorly in the transverse plane. ex: protract your clavicles at the acromioclavicular and sternoclavicular joints by crossing your arms

What are pivot joints?

Rounded or pointed surface fits into ring formed partly by bone and partly by ligament. -Uniaxial diarthrosis: rotation. -Atlanto-axial and radioulnar joints.

What is bursa?

Saclike structures called bursae (BER-se ̄ purses; singular is bursa) are strategically situated to alleviate friction in some joints, such as the shoulder and knee joints (see Figures 9.12 and 9.15c). 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. Bursae can be located between the skin and bones, tendons and bones, muscles and bones, or ligaments and bones. The fluid-filled bur- sal sacs cushion the movement of these body parts against one another.

medial meniscus

Semicircular piece of fibrocartilage (C-shaped). Its anterior end is attached to the anterior intercon- dylar fossa of the tibia, anterior to the anterior cruciate liga- ment. Its posterior end is attached to the posterior intercondy- lar fossa of the tibia between the attachments of the posterior cruciate ligament and lateral meniscus

What are special movements?

Special movements occur only at certain joints. They include elevation, depression, protraction, retraction, inversion, ever- sion, dorsiflexion, plantar flexion, supination, pronation, and opposition

What is the fibular collateral ligament?

Strong, rounded ligament on the lateral surface of the joint that extends from the lateral condyle of the femur to the lateral side of the head of the fibula (Figure 9.15a, e-h). It strengthens the lateral aspect of the joint.

What is the nerve and blood supply?

Synovial joints con- tain 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 phy- sician strikes the tendon below your kneecap to test your re- flexes. The spinal cord and brain respond by sending impulses through different nerves to the muscles to adjust body move- ments. Although many of the components of synovial joints are avas- cular, arteries in the vicinity send out numerous branches that penetrate the ligaments and articular capsule to deliver oxygen and nutrients. Veins remove carbon dioxide and wastes from the joints. The arterial branches from several different arteries typi- cally merge around a joint before penetrating the articular cap- sule. 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 capil- laries. Carbon dioxide and wastes pass from chondrocytes of ar- ticular cartilage into synovial fluid and then into veins; carbon dioxide and wastes from all other joint structures pass directly into veins.

What are tendon sheaths?

Tendon sheaths or synovial sheaths are tubelike bursae; they wrap around certain tendons that experience considerable fric- tion 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. The outer layer, known as the parietal layer, is attached to bone (see Figure 11.18a). Be- tween the layers is a cavity that contains a film of synovial fluid. A tendon sheath protects all sides of a tendon from friction as the tendon slides back and forth. 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). Ten- don 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 move- ment

What is the anterior cruciate ligament (ACL)?

The ACL limits hyperextension of the knee (which normally does not occur at this joint) and prevents the anterior sliding of the tibia on the femur. This ligament is stretched or torn in about 70% of all serious knee injuries.

What is the articular cartilage of the synovial joint?

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

What are synovial joints?

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 acces- sory ligaments.

What is the ligament of the articular capsule of the synovial joint?

The strength of these fiber bundles of the fibrous membrane, called ligaments (liga- bound or tied), is one of the principal mechanical factors that hold bones close together in a synovial joint.

What is synovial fluid?

The synovial membrane secretes synovial fluid (ov- egg), a vis- cous, clear or pale yellow fluid named for its similarity in appear- ance and consistency to uncooked egg white. Synovial fluid consists of hyaluronic acid secreted by synovial cells in the synovial mem- brane and interstitial fluid filtered from blood plasma. -ts functions in- clude 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 carti- lage. (Recall that cartilage is an avascular tissue, so it does not have blood vessels to perform the latter function.) Synovial fluid also contains phagocytic cells that remove microbes and the debris that results from normal wear and tear in the joint.

What is the synovial (joint) cavity?

The unique characteristic of a synovial joint is the presence of a space called a synovial cavity or joint cavity between the articulating bones. Because the synovial cavity allows considerable movement at a joint, all synovial joints are classified functionally as freely movable (diarthroses).

What is a synchondrosis?

a cartilaginous joint in which the connect- ing material is hyaline cartilage. -an immovable joint (synarthrosis). When bone elongation ceases, bone replaces the hyaline cartilage, and the synchondrosis becomes a synostosis, a bony joint.

What is a symphysis?

a cartilaginous joint in which the ends of the articu- lating bones are covered with hyaline cartilage, but a broad, flat disc of fibrocartilage connects the bones. -A symphysis is a slightly movable joint (amphiarthrosis).

What are cartilaginous joints?

a cartilaginous joint lacks a synovial cavity and allows little or no movement.

What is a suture?

a fibrous joint composed of a thin layer of dense irregular connective tis- sue; sutures occur only between bones of the skull. In older individuals, sutures are immovable (synarthroses), but in infants and children they are slightly movable (amphiarthroses) (Fig- ure 9.1b). Sutures play important roles in shock absorption in the skull.

What is a synostosis?

a joint in which there is a complete fusion of two separate bones into one.

What is retraction?

a movement of a protracted part of the body back to the anatomical position

What is eversion?

a movement of the sole laterally at the intertarsal joints

What is interosseous membrane?

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

How can joints be classified based on structure?

fibrous joints cartilaginous joints synovial joints

What are fibrous joints?

fibrous joints lack a synovial cavity, and the articulating bones are held very closely together by dense irregu- lar connective tissue. Fibrous joints permit little or no movement.

What is extension?

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 posi- tion after it has been flexed

What is a gomphosis or dentoalveolar joint?

in which a cone-shaped peg fits into a socket. The only examples of gomphoses in the human body are the articulations between the roots of the teeth and their sockets (alveoli) in the maxillae and mandible -permits no movement

What is plantar flexion?

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.

What are extracapsular accessory ligaments?

lie outside the articular cap- sule. Examples are the fibular and tibial collateral ligaments of the knee joint.

What is pronation?

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

What is supination?

movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly

What is inversion?

movement of the sole medially at the intertarsal joints

What are the 6 types of synovial joints?

plane joint hinge joint pivot joint condyloid or ellipsoidal joint saddle joint ball and socket joint

What is dorsiflexion?

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)

What kind of plane do flexion and extension occur along?

sagittal plane

How can joints be classified based on function as?

synarthrosis amphiarthrosis diarthrosis

What are the types of cartilaginous joints?

synchondrosis symphysis

What are the types of the suture?

synostosis frontal or metopic sututure

What are the parts of the synovial joints?

synovial (joint) cavity articular cartilage articular capsule fibrous membrane ligament synovial membrane articular fat pad synovial fluid accessory ligaments: extracapsular and intracapsular ligaments articular discs (menisci) labrum nerve and blood supply

What are cartilaginous joints?

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

What are fibrous joints?

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

What are the 3 types of fibrous joints?

sutures, syndesmoses, gomphoses

What is a synarthrosis?

An immov- able joint. The plural is synarthroses.

What is rotation?

In rotation (roˉ-TAˉ -shun; rota- revolve), a bone revolves around its own longitudinal axis.

What is an adduction?

adduc- tion (ad-DUK-shun; ad- toward) or ulnar deviation is the move- ment of a bone toward the midline.

What is the synovial membrane of the articular capsule?

composed of areolar connective tissue with elastic fibers.