Ch. 9 Articulations

Lumbosacral

(1) Between body of fifth lumbar vertebra and base of sacrum. (2) Between inferior articular facets of fifth lumbar vertebra and superior articular facets of first verebra of sacrum. Structural: cartilaginous (symphysis) between body and base; synovial (planar) between articular facets. Functional: ampiarthrosis between body and base; diarthrosis between articular facets. Movement: flexion, extension, lateral flexion, and rotation of vertebral column.

Atlanto-axial

(1) Between dens of axis and anterior arch of atlas. (2) Between lateral masses of atlas and axis. Structural: synovial (pivot) between dens and anterior arch; synovial (planar) between lateral masses. Functional: diarthrosis. Movement: rotation of head.

Ankle (talocrural)

(1) Between distal end of tibia and its medial malleolus and talus. (2) Between lateral malleolus of fibula and talus. Structural: synovial (hinge). Functional: diarthrosis. Movement: dorsiflexion and plantar flexion of foot.

Vertebrocostal

(1) Between facets of heads of ribs and facets of bodies of adjacent thoracic vertebrae and intervertebral discs between them. (2) Between articular part of tubercles of ribs and facets of transverse processes of thoracic vertebrae. Structural: synovial (planar). Functional: diarthrosis. Movement: slight gliding.

Intervertebral

(1) Between vertebral bodies. (2) Between vertebral arches. Structural: cartilaginous (symphysis) between vertebral bodies; synovial (planar) between vertebral arches. Functional: amphiarthrosis between vertebral bodies; diarthrosis between vertebral arches. Movement: flexion, extension, lateral flexion, and rotation of vertebral column.

3. Diarthrosis

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

2. Amphiarthrosis

(on both sides.) A slightly movable joint.

The structural classification of joints is based on (1) the presence or absence of a space between the articulating bones, called a synovial cavity, and (2) the type of connective tissue that holds the bones together. Structurally, joints are classified as:

1. Fibrous joints, 2. Cartilaginous joints, 3. Synovial joints

Movements at synovial joints are grouped into four man categories:

1. Gliding, 2. Angular movements, 3. Rotation, 4. Special movements that occur only at certain joints.

The functional classificatoin of joints relates to the degree of movement they permit. Functionally, joints are classified as:

1. Synarthrosis, 2. Amphiarthrosis, 3. Diarthrosis

Two types of cartilaginous joints:

1. Synchondroses, 2. Symphyses

Coracohumeral ligament

A ligament that strengthens the superior part of the articular capsule and extends from the coracoid process of the scapula to the greater tubercle of the humerus. The ligament strengthens the superior part of the articular capsule and reinforces the anterior aspect of the articular capsule.

1. Synarthrosis

An immovable joint.

Examples of hyperextension include:

Bending the head backward. Bending the trunk backward (as in a back bend). Moving the humerus backward at the shoulder joint, as in swinging the arms backward while walking. Moving the palm backward at the wrist joint. Moving the femur backward at the hip joint, as in walking.

Examples of flexion (extension is simply the reverse of these movements):

Bending the head toward the chest. Bending the trunk forward - like bending over to touch your toes. Moving the humerus forward at the shoulder joint, as in swinging the arms forward while walking. Moving the forearm toward the arm at the elbow joint. Moving the palm toward the forearm at the wrist joint, as in preparing to shoot a basketball. Bending at the interphalangeal joints between phalanges, as when making a fist of the fingers or when curling the toes. Moving the femur forward at the hip joint, as in walking. Moving the leg toward the thigh, as occurs when bending the knee.

Acromioclavicular

Between acromion of scapula and acromial end of clavicle. Structural: synovial (plane). Functional: diarthrosis. Movement: gliding and rotation of scapula on clavicle.

Pubic symphysis

Between anterior surfaces of hip bones. Structural: cartilaginous (symphysis). Functional: amphiarthrosis. Movement: slight movements (even more so during pregnancy).

Sacroiliac

Between auricular surfaces of sacrum and ilia of hip bones. Structural: synovial (plane). Functional: diarthrosis. Movement: Slight gliding (even more so during pregnancy).

Wrist (radiocarpal)

Between distal end of radius and scaphoid, lunate, and triquetrum of carpus. Structural: synovial (condyloid). Functional: diarthrosis. Movement: flexion, extension, abduction, circumduction, and slight hyperextension of wrist.

Metacarpophalangeal and metatarsophalangeal

Between heads of metacarpals (or metatarsals) and bases of proximal phalanges. Structural: synovial (condyloid). Functional: diarthrosis. Movement: flexion, extension, abduction, adduction, and circumduction of phalanges,

Interphalangeal

Between heads of phalanges and bases of more distal phalanges. Structural: synovial (hinge). Functional: diarthrosis. Movement: flexion and extension of phalanges.

Intercarpal

Between proximal row of carpal bones, distal row of carpal bones, and between both rows of carpal bones (midcarpal joints). Structural: synovial (plane), except for hamate, scaphoid, and lunate (midcarpal) joint, which is synovial (saddle). Functional: diarthrosis. Movement: gliding plus flexion, extension, abduction, adduction, and slight rotation at midcarpal joints.

Suture

Between skull bones. Structural: fibrous. Functional: amphiarthrosis and synarthrosis. Movements: none.

Sternoclavicular

Between sternal end of clavicle, manubrium of sternum, and first costal cartilage. Structural: synovial (plane, pivot). Functional: diarthrosis. Movement: gliding, with limited movements in nearly every direction.

Sternocostal

Between sternum and first seven pairs of ribs. Structural: cartilaginous (synchondrosis) between sternum and first pair of ribs; synovial (plane) between sternum and second through seventh pair of ribs. Functional: synarthrosis between sternum and first pair of ribs; diarthrosis between sternum and second through seventh pair of ribs. Movement: None between sternum and first pair of ribs; slight gliding between sternum and second through seventh pair of ribs.

Atlanto-occipital

Between superior articular facets of atlas and occipital condyles of occipital bone. Structural: synovial (condyloid). Functional: diarthrosis. Movements: Flexion and extension of head; slight lateral flexion of head to either side.

Tarsometatarsal

Between three cuneiforms of tarsus and bases of five metatarsal bones. Structural: synovial (plane). Functional: diarthrosis. Movement: slight gliding.

Carpometacarpal

Carpometacarpal joint of thumb between trapezium of carpus and first metacarpal; carpometacarpal joints of remaining digits formed between carpus and second through fifth metacarpals. Structural: synovial (saddle) at thumb; synovial (plane) at remaining digits. Functional: diarthrosis. Movement: flexion, extension, abduction, adduction, and circumduction at thumb; gliding at remaining digits.

Patellar ligament

Continuation of the insertion tendon of the quadriceps femoris (anterior thigh muscles) that extends from the patella to the tibial tuberosity. The ligament is separated from the synovial membrane of the joint by an infrapatellar fat pad.

Arcuate popliteal ligament

Extends from the lateral condyle of the femur to the head of the fibula. It strengthens the posterior surface of the joint.

Acetabular labrum

Fibrocartilage rim attached to the margin of the acetabulum that increases the depth of the acetabulum. As a result, dislocation of the femur is rare.

Ligament of the head of the femur

Flat band that extends from the fossa of the acetabulum to the fovea capitis, a small depression in the center of the head of the femur.

Bursae

Four bursae help reduce friction where body parts move across the shoulder joint. They are the subscapular bursa, subdeltoid bursa, subacromial bursa, and subcoracoid bursa.

Medial and lateral patellar retinacula

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

In the limbs, rotation is defined relative to the midline.

If the anterior surface of a bone of the limb is turned toward the midline,the movement is called *medial rotation*. If the anterior surface of the bone of a limb is turned away from the midline, the movement is called *lateral rotation*.

Saddle joint

In this joint the articular surface of one bone is saddle-shaped (the concave surface); the articular surface of the other bone fits into the "saddle" like a rider sitting on a horse. Saddle joints permit movement around three axes: side to side, up and down, and rotation. Like a condyloid joint, movement at a saddle joint are around two axes (flexion-extension and abduction-adduction) plus limited circumduction. An example of a saddle joint is the carpometacarpal joint between the trapezium of the wrist and metacarpal of the thumb.

Condyloid joint

In this joint the convex oval-shaped projection of one bone fits into the oval-shaped depression of another bone. This joint permits movement around two axes (flexion-extension and abduction-adduction), plus limited circumduction. Examples of condyloid joints are the wrist and the metacarpophalangeal joints (between the metacarpals and phalanges) of the second through fifth fingers.

Hinge joints

In this joint the convex surface of one bone fits into the concave surface of another bone. 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. An axis is a straight line around which a bone moves. Hinge joints allow motion along a single axis. Hinge joints permit only flexion and extension. Examples of hinge joints are the knee, elbow, ankle, and interphalangeal joints (between the phalanges of the fingers and toes).

Pivot joint

In this joint the rounded or pointed surface of one bone articulates with a ring formed partly by another bone and partly by a ligament. This joint allows rotation only around its own 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", and the radioulnar joints that enable the palms to turn anteriorly and posteriorly as the head of the radius pivots around its axis in the radial notch of the ulna.

Transverse ligament of the acetabulum

Ligament that crosses over the inferior acetabulum to connect with the ligament of the head of the femur and the articular capsule.

Fibular collateral ligament

Ligament that extends from the lateral condyle of the femur to the head of the fibula. It strengthens the lateral aspect of the joint.

Oblique popliteal ligament

Ligament that extends from the lateral condyle of the femur to the head of the medial condyle of the tibia. The ligament strengthens the posteriior surfaces of the joint.

Radial collateral ligament

Ligament that extends from the lateral epicondyle of the humerus to the anular ligament of the radius and the radial notch of the ulna.

Tibial collateral ligament

Ligament that extends from the medial condyle of the femur to the medial condyle of the tibia. It strengthens the medial surface of the joint. The tibial collateral ligament is firmly attached to the medial meniscus. Because the tibial collateral ligament is firmly attached to the medial meniscus, tearing of the ligament frequently results in tearing of the meniscus and damage to the anterior cruciate ligament.

Ulnar collateral ligament

Ligament that extends from the medial epicondyle of the humerus to the coronoid process and olecranon of the ulna.

Intrascapular ligaments

Ligaments within the articular capsule that connect the tibia and femur. The anterior and posterior *cruciate ligaments* are named based on their attachment sites on the tibia and because they cross one another on their way to their destination on the femur.

Accessory ligaments

Many synovial joints contain these and they lie outside and inside the articular capsule.

Articular fat pads

Many synovial joints include cushioning accumulations of adipose tissue called this.

Glenoid labrum

Narrow rim of fibrocartilage around the edge of the glenoid cavity that slightly deepens and enlarges the socket.

Iliofemoral ligament

Portion of the articular capsule that extends from the ilium of the hip bone to the intertrochanteric line of the femur. This ligament is said to be the body's strongest and prevents hyperextension of the femur at the hip joint during standing.

Ischiofemoral ligament

Portion of the articular capsule that extends from the ischial wall of the acetabulum to the neck of the femur. This ligament slackens during adduction, tenses during abduction, and strengthens the articular capsule.

Pubofemoral ligament

Portion of the articular capsule that extends from the pubic wall of the acetabulum to the neck of the femur. This ligament prevents overabduction of the femur at the hip joint and strengthens the articular capsule.

Radioulnar

Proximal radioulnar joint between head of radius and radial notch of ulna; distal radioulnar joint between ulnar notch of radius and head of ulna. Structural: synovial (pivot). Functional: diarthrosis. Movement: rotation of forearm.

Tibiofibular

Proximal tibiofibular joint between lateral condyle of tibia and head of fibula; distal tibiofibular joint between distal end of fibula and fibular notch of tibia. Structural: synovial (plane) at proximal joint; fibrous (syndesmosis) at distal joint. Functional: diarthrosis at proximal joint; ampiarthrosis at distal joint. Movement: slight gliding at proximal joint; slight rotation of fibula during dorsiflexion of foot.

Synovial fluid

Secreted by the synovial membrane. It forms a thin film over the surfaces within the articular capsule. The viscous, clear fluid was named for its similarity in appearance and consistency to uncooked egg white (albumin).

Bursae

Several important bursae are associated with the knee to help relieve friction at the knee joint. For example, the *prepatellar bursa* located between the patella and skin, is often damaged when you bump the anterior knee.

Synostosis

Some sutures, although present during childhood, are completely replaced in the adult by osseous tissue across the suture line. Is classified as a synarthrosis because it is immovable.

Selected joints of the appendicular skeleton:

Sternoclavicular, Acromioclavicular, Radioulnar, Wrist (radiocarpal), Intercarpal, Carpometacarpal, Metacarpophalangeal and metatarsophalangeal, Interphalangeal, Sacroiliac, Pubic symphysis, Tibiofibular, Ankle (talocrural), Intertarsal, Tarsometatarsal

Anular ligament of the radius

Strong band that encircles the head of the radius. It holds the head of the radius in the radial notch of the ulna.

Intertarsal

Subtalar joint between talus and calcaneus of tarsus; talocalcaneonavicular joint between talus and calcaneus and navicular of tarsus; calcaneocuboid joint between calcaneus and cuboid of tarsus. Structural: synovial (plane) at subtalar and calcaneocuboid jooints; synovial (saddle) at talocalcaneonavicular joint. Functional: diarthrosis. Movement: inversion and eversion of foot.

Selected joints of the axial skeleton:

Suture, Atlanto-occipital, Atlanto-axial, Intervertebral, Vertebrocostal, Sternocostal, Lumbosacral

Articular capsule

The anterior part extends from the humerus to the ulna and the anular ligament that encircles the head of the radius. The posterior part extends from the capitulum, olecranon, fossa, and lateral epicondyle of the humerus to the anular ligament of the radius, the olecranon of the ulna, and the ulna posterior to the radial notch.

Plane joint

The articulating surfaces of bones in this joint are flat or flightly curved. Plane joints primarily permit side to side and back and forth gliding movements between the flat surfaces of bones, but they may rotate against one another. Examples 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), and vertebrocostal joints (between the ribs and transverse processes of thoracic vertebrae).

2. Cartilaginous joints

The bones are held together by cartilage, and there is no synovial cavity.

1. Fibrous joints

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

3. Synovial joints

The bones are united by the dense connective tissue of an articular capsule and often by accessory ligaments, and there is a synovial cavity.

Articular capsule

The capsule is weak and incomplete, but it is strengthened by muscle tendons and ligaments associated with the joint.

Synovial membrane

The inner layer of the articular capsule.and is composed of aerolar connective tissue.

Synovial cavity

The unique characteristic of this cavity is the presence of a space between the articulating bones.

Ball-and-socket joint

This joint consists of the ball-like surface of one bone fitting into a cuplike depression of another bone. Such joints permit movement around three axes (flexion-extension, abduction-adduction, and rotation). 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 cavitiy of the scapula. At the hip joint the head of the femur fits into the acetabulum of the hip bone.

Articular (joint) capsule

This sleevelike capsule surrounds the synovial joint, encloses the synovial cavity, and unites the articulating bones.

Glenohumeral ligaments

Three thickenings of the articular capsule over the anterior surface of the joint that extend from the glenoid cavity to the lesser tubercle and anatomical neck of the humerus. These ligaments are often indistinct or absent and provide only minimal strength. They play a role in joint stabilization when the humerus approaches or exceeds its limits of motion.

Articular discs (menisci)

Two fibrocartilage discs between the tibial and femoral condyles help compensate for the irregular shapes of the bones and circulate synovial fluid.

Articular capsule

Very dense and strong capsule that extends from the rim of the acetabulum to the neck of the femur. This capsule, which is one of the strongest structures in the body, consists of overlapping circular and longitudinal fibers. The circular fibers, called the zona orbicularis, form a collar around the neck of the femur.

3. Rotation

a bone revolves around its own longitudinal axis. One example is turning the head from side to side (between the atlas and axis), as when you shake your head "no." Another is turning the trunk from side to side at the intervertebral joints while keeping the hips and lower limbs in the anatomical position.

Interosseous membrane

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

The midline of the body is NOT used as a point of reference for

abduction and adduction of the fingers.

Synovial fluid

also contains phagocytic cells that remove microbes and the debris that results from normal wear and tear in the joint. When a synovial joint is immobile for a time, the fluid becomes quite viscous (gel-like), but as joint movement increases, the fluid thins, becoming less viscous. One of the benefits of warming up before exercise is that it stimulates the production and secretion of synovial fluid; more fluid means less stress on the joints during exercise.

Articular menisci

also help to maintain the stability of the joint and direct the flow of synovial fluid across the articular surfaces of the joint.

Bursae

are not strictly parts of synovial joints, but they do resemble joint capsules because their walls consist of connective tissue lined by a synovial membrane. They are also filled with a small amount of fluid that is similar to synovial fluid.

Articular menisci

are pads of fibrocartilage inside some synovial joints, such as the knee, and lie between the articular surfaces of the bones and are attached to the fibrous membrane.

Bursae

are saclike structures that are strategically situated to alleviate friction in some joints, such as the shoulder and knee joints.

The ____ capsule is composed of two layers, an outer fibrous membrane and an inner synovial membrane.

articular

The bones at a synovial joint are covered by a layer of hyaline cartilage called ____ cartilage that provides a smooth, slippery surface that reduces friction between bones in the joint during movement and helps to absorb shock.

articular

The anatomical components of the shoulder joint include the following:

articular capsule, coracohumeral ligament, glenohumeral ligaments, glenoid labrum, bursae.

Anatomical components of the hip joint include the following:

articular capsule, iliofemoral ligament, pubofemoral ligament, ischiofemoral ligament, ligament of teh head of the femur, acetabular labrum, transverse ligament of the acetabulum.

Anatomical components of the knee joint include the following:

articular capsule, medial and lateral patellar retinacula, patellar ligament, oblique popliteal ligament, arcuate popliteal ligament, tibial collateral ligament, fibular collateral ligament, intracapsular ligaments, cruciate ligaments, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), articular discs (menisci), medial meniscus, lateral meniscus, bursae, prepatellar bursa.

Anatomical components of the elbow joint include the following:

articular capsule, ulnar collateral ligament, radial collateral ligament, anular ligament of the radius.

When we say bone ____ with another bone, we mean that the bones form a joint.

articulates

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.

The *posterior cruciate ligament (PCL)*

extends anteriorly and medially from the posterior intercondylar area of the tibia to the lateral surface of the medial condyle of the femur.

The *anterior cruciate ligament (ACL)*

extends posteriorly and laterally from a point anterior to the intercondylar area of the tibia to the medial surface of the lateral condyle of the femur.

The elbow joint allows

flexion and extension of the forearm.

The hip joint allows

flexion, extension, abduction, adduction, circumduction, medial rotation, and lateral rotation of the thigh.

The shoulder joint allows

flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction of the arm.

The knee joint allows

flexion, extension, and slight medial rotation, and lateral rotation of the leg in the flexed position.

Synovial fluid

forms a thin film over the surfaces within the articular capsule that reduces friction by lubrication of the joint and absorbs shocks; it also supplies oxygen and nutrients to and removes carbon dioxide and metabolic wastes from the articular cartilage. (Recall that cartilage is an avascular tissue, so it does not have blood vessels to perform the latter function.)

The shoulder joint has more

freedom of movement than any other joint in the body.

The frontal bone grows in halves that are joined together by a suture that usually completely fuses by age 6. If the suture persists beyond age 6, it is called:

frontal or metopic suture

Tendon sheaths are also found

in the fingers and toes, where there is a great deal of movement.

An example of syndesmosis is a *gomphosis*

in which a cone-shaped peg fits into a socket. The only examples of gomphoses are the articulations between the roots of the teeth and their sockets (alveoli) in the maxillae and mandible. The dense connective tissue between a tooth and its socket is the thin periodontal ligament. A gomphosis is classified functionally as a synarthrosis, an immovable joint.

There are two principal ____ joints in the human body. One occurs between the radius and ulna in teh forearm and the other occurs between the tibia and fibula in the leg.

interosseous memrane

Plantar flexion

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

Hip joint

is a ball-and-socket joint formed by the head of the femur and the acetabulum of the hip bone.

Shoulder joint

is a ball-and-socket joint formed by the head of the humerus and the glenoid cavity of the scapula. It also is referred to as the glenohumeral joint.

1. Synchondrosis

is a cartilaginous joint in which the connecting material is hyaline cartilage. An example is the epiphyseal plate that connects the epiphysis and diaphysis of a growing bone.

2. Symphysis

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

Depression

is a downward movement of a part of the body, such as opening the mouth to depress the mandible or returning shrugged shoulders to the anatomical position to depress the scapula.

Suture

is a fibrous joint composed of a thin layer of dense connective tissue. Sutures occur only between bones of the skull. Sutures play important roles in shock absorption in the skull.

Syndesmosis

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

Elbow joint

is a hinge joint formed by the trochlea of the humerus, the trochlear notch of the ulna, and the head of the radius.

Protraction

is a movement of a part of the body anteriorly in the transverse plane. You can protract your mandible at the temporomandibular joint by thrusting it outward. Its opposing movement is *retraction*.

Retraction

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

Supination

is a movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly, or forward. This position of the palms is one of the defining features of the anatomical position. Its opposing movement is *pronation*.

Pronation

is a movement of the forearm so that the distal end of the radius crosses over the distal end of the ulna and the palm is turned posteriorly.

Eversion

is a movement of the sole laterally at the intertarsal joints so that it faces away from the other foot. Physical therapists also refer to eversion of the feet as pronation.

Inversion

is a movement of the sole of the foot medially at the intertarsal joints (between the tarsals) so that it faces the other foot. Its opposing movement is *eversion*. Physical therapists also refer to inversion of the feet as pronation.

A joint (also called an articulation)

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

1. 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. 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.

Rotator cuff injury

is a strain or tear in the rotator cuff muscles and is a common injury among baseball pitchers, volleyball players, racket sports players, swimmers, and violinists due to shoulder movements that involve vigorous circumduction. It also occurs as a result of wear and tear, aging, trauma, poor posture, improper lifting, and repetitive motions in certain jobs.

Articular capsule

is a thin, loose sac that completely envelops the joint and extends from the glenoid cavity to the anatomical neck of the humerus.

Elevation

is an upward 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, or shrugging the shoulders at the acromioclavicular joint (between the acromion of the scapula and the clavicle) to elevate the scapula. Its opposing movement is *depression*.

The *lateral meniscus*

is attached anteriorly to the tibia and the anterior cruciate ligament, and posteriorly to the tibia and medial meniscus.

The *medial meniscus*

is attached to the anterior intercondylar fossa of the tibia and to the posterior intercondylar fossa of the tibia between the attachments of the posterior cruciate ligament and lateral meniscus.

Hyperextension

is continuation of extension beyond the anatomical position.

Circumduction

is movement of the distal end of a body part in a circle. It is not an isolated movement by itself but rather a continuous sequence of flexion, abduction, extension, and adduction.

Lateral flexion

is movement which occurs along the frontal plane and involves the intervertebral joints. An example is bending of the trunk at the waist (a side bend).

Knee joint

is the largest and most complex joint of the body, is a modified hinge joint.

Abduction

is the movement of a bone away from the midline.

Adduction

is the movement of a bone toward the midline.

Opposition

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

Extension

is the movement that returns body parts to the anatomical position.

Adduction

is the movement that returns each abduction movement and the body parts back to the anatomical position.

The fibers of some fibrous membranes are arranged in parallel bundles that are highly adapted for resisting strains. Such fiber bundles, called ____, are one of the principal mechanical factors that hold bones close together in a synovial joint.

ligaments

Cartilaginous joint

like a fibrous joint lacks a synovial cavity and allows little or no movement. Here the articulating bones are tightly connected, either by hyaline cartilage or fibrocartilage.

The *ACL*

limits hyperextension of the knee and prevents the anterior sliding of the tibia on the femur. This ligament is stretched or torn in about 70 percent of all serious knee injuries.

Examples of circumduction are

moving the humerus in a circle at the shoulder joint, moving the hand in a circle at the wrist joint, moving the thumb in a circle, moving a finger in a circle, and moving the femur in a circle at the hip joint.

Examples of abduction include

moving the humerus laterally at the shoulder joint, moving the palm laterally (away from the body) at the wrist joint, and moving the femur laterally at the hip joint.

4. Special movements

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

Hyperextension

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

Types of synovial joints divided into six categories based on type of movement:

plane joint, hinge joint, pivot joint, condyloid joint, saddle joint, or ball-and-socket joint.

The *PCL*

prevents the posterior sliding of the tibia when the knee is flexed. This is important when walking down stairs or a steep incline.

Tendon sheaths

reduce friction at joints. These tubelike bursae wrap around tendons that experience considerable friction.

Dorsiflexion

refers to bending of the foot at the ankle in the direction of the dorsum (superior surface). Dorsiflexion occurs when you stand on your heels. Its opposing movement is *plantar flexion*.

Range of motion (ROM)

refers to the range, measured in degrees in a circle, through which the bones of a joint can be moved.

Flexion and extension usually occur along the

sagittal plane, although there are a few exceptions. An example is movement of the trunk sideways to the right or left at the waist as in a side bend which is *lateral flexion*

The three types of fibrous joints are:

sutures, syndesmoses, and interosseous membranes

All ____ occur in the midline of the body. The pubic symphysis between the anterior surfaces of the hip bones is one example of a symphysis. This type of joint is also found at the sternal angle, the junction of the maubrium and body of the sternum, and at the intervertebral jooints between the bodies of vertebrae. A portion of the intervertebral disc is composed of fibrocartilage.

symphyses.

A ____ is classified functionally as an amphiarthrosis, a slightly movable joint.

symphysis

Functionally, a ____ is an immovable joint (synarthrosis). When bone elongation ceases, osseous tissue replaces the hyaline cartilage, and the ____ becomes an immovable synostosis, a bony joint.

synchondrosis

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

synovial

Examples of accessory ligaments inside the articular capsule are

the anterior and posterior cruciate ligaments of teh knee joint.

Examples of accessory ligaments that lie outside the articular capsule are

the fibular and tibial collateral ligaments of the knee joint.

Both abduction and adduction usually occur along

the frontal plane.

Although the shoulder and hip joints are both ball-and-socket joints,

the hip joint does not have as wide aa range of motion due to tension of the hip joint's strong ligaments.

In *flexion*

there is a decrease in the angle between articulating bones.

In *extension*

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.

2. Angular movements

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

fibrous membrane

usually consists of dense connective tissue (mostly collagen fibers) that attaches to the periosteum of the articulating bones. The flexibility of the fibrous membrane permit considerable movement at a joint while its great tensile strength (resistance to stretching) helps prevent the bones from dislocating.

Articular menisci

usually subdivide the synovial cavity into two separate spaces. This separaton can allow separate movements to occur in each space.

Tendon sheaths are found

where tendons pass through synovial cavities, such as the tendon of the briceps brachii muscle at the shoulder joint.