No. 2 No. 2

The IntroductionThe Introduction

of Arthrologyof Arthrology

Chapter 2 ArthrologyChapter 2 Arthrology

Section 1 IntroductionSection 1 Introduction

The bones are connected together by fibrThe bones are connected together by fibrous, cartilaginous or osseous tissues at difous, cartilaginous or osseous tissues at different parts of their surfaces, and such a cferent parts of their surfaces, and such a connection is designated by the name of onnection is designated by the name of jojointint or or articulationarticulation..

According to the movement they are classAccording to the movement they are classified into two types of joints, i.e. synarthrified into two types of joints, i.e. synarthroses (syn=together; arthron=joint) and diaoses (syn=together; arthron=joint) and diarthroses. rthroses.

ⅠⅠ. . SynarthrosesSynarthroses

The The synarthrosessynarthroses (immovable articu (immovable articulations) include the fibrous joints, the cartlations) include the fibrous joints, the cartilaginous joints and synostoses. However, ilaginous joints and synostoses. However, slight movement is, in fact, permitted in sslight movement is, in fact, permitted in some synarthroses.ome synarthroses.

ⅠⅠ) The ) The FibrousFibrous Joints Joints The The fibrous jointsfibrous joints include all the arti include all the arti

culations in which the bones are held tighculations in which the bones are held tightly together by fibrous connective tissue. tly together by fibrous connective tissue. The bones are united by fibrous tissue witThe bones are united by fibrous tissue without any cavity. There are two types of fihout any cavity. There are two types of fibrous joints, brous joints, suturessutures and and syndesmosessyndesmoses, de, depending in part on the length of the connepending in part on the length of the connective tissue fibers that hold the bones togective tissue fibers that hold the bones together.ther.

1. 1. SuturesSutures

The separated bones are held together The separated bones are held together by a thin layer of fibrous tissue. The union by a thin layer of fibrous tissue. The union is extremely tight and there is little or no is extremely tight and there is little or no movement between the bones. This kind movement between the bones. This kind of joint is found only between the flat of joint is found only between the flat bones of the skull and can be fused by bones of the skull and can be fused by ossification from the early 20s and ossification from the early 20s and progresses throughout the life.progresses throughout the life.

2. 2. SyndesmosesSyndesmoses

The bones are united by a ligament oThe bones are united by a ligament or a sheet of fibrous tissue, e.g., the yellow r a sheet of fibrous tissue, e.g., the yellow ligaments join the adjacent two vertebral ligaments join the adjacent two vertebral arches, and the interoseous membrane joiarches, and the interoseous membrane joins the radius with the ulna.ns the radius with the ulna.

Bones joined by syndesmoses are not Bones joined by syndesmoses are not held as firmly as those joined by sutures. held as firmly as those joined by sutures. Syndesmoses can permit some movement.Syndesmoses can permit some movement.

ⅡⅡ) ) Cartilaginous JointsCartilaginous Joints

The bones are united by cartilage. They alThe bones are united by cartilage. They allow little or no movement.low little or no movement.

There are two types of cartilaginous jointThere are two types of cartilaginous joints: s:

synchondrosessynchondroses

symphysessymphyses..

1. 1. SynchondrosesSynchondroses The bones of a synchondrosis joint are jointeThe bones of a synchondrosis joint are jointe

d by hyaline cartilage.For example, the epiphysid by hyaline cartilage.For example, the epiphysial cartilage plate connects the ends and the shaft al cartilage plate connects the ends and the shaft of a long bone.of a long bone.

Many synchondroses are temporary joints, Many synchondroses are temporary joints, with the cartilage eventually being replaced by with the cartilage eventually being replaced by bone. This replacement occurs between the epipbone. This replacement occurs between the epiphyses and the diaphysis of long bones (where thhyses and the diaphysis of long bones (where the epiphyseal cartilages are replaced) and betweee epiphyseal cartilages are replaced) and between certain skull bones. The joints formed between certain skull bones. The joints formed between the first ten ribs and their costal cartilages are n the first ten ribs and their costal cartilages are permanent synchondroses.permanent synchondroses.

2. 2. SymphysesSymphyses The connecting material is a broad, flat The connecting material is a broad, flat

disc of fibrocartilage.disc of fibrocartilage.

This kind of joint is found between the This kind of joint is found between the bodies of vertebrae. The pubic symphysis ibodies of vertebrae. The pubic symphysis is another example of these joints. The syms another example of these joints. The symphysis does not ossify throughout the life.physis does not ossify throughout the life.

ⅢⅢ) ) SynostosesSynostoses

The bones are united by the ossificatioThe bones are united by the ossification of the fibrous joint or synchondrosis betn of the fibrous joint or synchondrosis between them, e.g., the synostoses between tween them, e.g., the synostoses between the ilium, ischium and pubis of the hip bohe ilium, ischium and pubis of the hip bone.ne.

ⅡⅡ. . DiarthrosesDiarthroses

The The DiarthrosesDiarthroses (movable articulations, syn (movable articulations, synovial joints) there is a space between the articuovial joints) there is a space between the articulating bones, called the synovial cavity. This kilating bones, called the synovial cavity. This kind of joints normally provide free movement.nd of joints normally provide free movement.

The bones are connected by the joint capsule The bones are connected by the joint capsule and ligament. There is a space between the articuand ligament. There is a space between the articulating bones, called the synovial cavity. This kinlating bones, called the synovial cavity. This kind of joints normally provide free movement. We d of joints normally provide free movement. We called them as called them as Synovial JointsSynovial Joints

ⅠⅠ) ) The Essential Structures of a SynThe Essential Structures of a Synovial Jointovial Joint

The essential structures are as follows:The essential structures are as follows:

Articular surface,Articular surface,

Articular capsule,Articular capsule,

Articular cavity.Articular cavity.

1. The articular surfaces1. The articular surfaces

They are usually covered by the articular They are usually covered by the articular cartilage. The cartilage. The articular cartilagearticular cartilage is a thi is a thin layer of hyaline cartilage that covers the n layer of hyaline cartilage that covers the smooth articular surfaces of the bones. It ismooth articular surfaces of the bones. It is very smooth but uneven in the thicknesss very smooth but uneven in the thickness..

2. The articular (joint) capsule2. The articular (joint) capsule The articular capsule is a double-layered memThe articular capsule is a double-layered mem

brane that surrounds and encloses the joint. It ibrane that surrounds and encloses the joint. It is attached to the periphery of the articular surfs attached to the periphery of the articular surface and adjacent bone surface. ace and adjacent bone surface.

The outer layer of the capsule (The outer layer of the capsule (fibrous membrfibrous membraneane) is formed by dense connective tissue who) is formed by dense connective tissue whose fibers are firmly joined to the periosteum of se fibers are firmly joined to the periosteum of the bones and is riched in blood vessels and nethe bones and is riched in blood vessels and nerves. Its thickness is corresponding to the functrves. Its thickness is corresponding to the functions of the joint.ions of the joint.

The inner layer of the articular capsule is referrThe inner layer of the articular capsule is referred to as the ed to as the synovial membranesynovial membrane. It consists of . It consists of lose connective tissue whose inner surface is wlose connective tissue whose inner surface is well supplied with capillaries. The membrane, well supplied with capillaries. The membrane, which is often thrown into folds that project into hich is often thrown into folds that project into the joint cavity, invests the inside of the fibrouthe joint cavity, invests the inside of the fibrous membrane, except for the surface of the artics membrane, except for the surface of the articular cartilages. It is very thin, glistening and sliular cartilages. It is very thin, glistening and slippery.ppery.

The synovial membrane secretes a thick fluiThe synovial membrane secretes a thick fluid called d called synovial fluidsynovial fluid (synovia). Synovial flui (synovia). Synovial fluid provides nourishment to the articular cartilagd provides nourishment to the articular cartilages, and lubricates the joint surfaces.es, and lubricates the joint surfaces.

3. The articular (joint) cavity3. The articular (joint) cavity

It is a closed cavity formed by the synoviaIt is a closed cavity formed by the synovial membrane and the articular cartilage. It contal membrane and the articular cartilage. It contains a proper amount of synovia. Its pressure is ins a proper amount of synovia. Its pressure is negative to the atmosphere pressure.negative to the atmosphere pressure.

ⅡⅡ) The Accessory Structures of Sy) The Accessory Structures of Synovial Joints novial Joints

The accessory structures are as follows:The accessory structures are as follows:

The The ligamentsligaments

The The articular discarticular disc (or cartilage) (or cartilage)

The The articular labrumarticular labrum (lip) (lip)

1. The 1. The ligamentsligaments The joints are usually strengthened by The joints are usually strengthened by

accessory ligaments which are either insiaccessory ligaments which are either inside or outside the joint (the intracapsular ade or outside the joint (the intracapsular and extracapsular ligament). These ligamend extracapsular ligament). These ligaments are designed to limit movements of thnts are designed to limit movements of the joint in undesirable direction.e joint in undesirable direction.

2. The 2. The articular discarticular disc (or cartilage) (or cartilage) It is usually a fibrocartilage and divides the It is usually a fibrocartilage and divides the

joint cavity partially or completely into two joint cavity partially or completely into two parts. parts.

Functions: It makes the articular surfaces mFunctions: It makes the articular surfaces more fitting with each other and diminishes the sore fitting with each other and diminishes the shock of the joint.hock of the joint.

3. The 3. The articular labrumarticular labrum (lip) (lip) It is a pliable, fibrocartilaginous ring that heIt is a pliable, fibrocartilaginous ring that he

lps to deepen the articular surface for the bonelps to deepen the articular surface for the bones, e.g., the labrum of the glenoid cavity of the ss, e.g., the labrum of the glenoid cavity of the scapula.capula.

ⅢⅢ) ) The Movement of JointThe Movement of Joint

The basic movements of joints are as follows: The basic movements of joints are as follows:

1. Flexion1. Flexion and and extensionextension

2. Adduction2. Adduction and and abductionabduction

3. 3. RotationRotation

4. 4. CircumductionCircumduction

1. Flexion1. Flexion and and extensionextension These two antagonistic movements are performeThese two antagonistic movements are performe

d in the coronal axis.d in the coronal axis.TheThe flexionflexion decreases the angle between the adjo decreases the angle between the adjo

ining bones, whereas the ining bones, whereas the extensionextension increases t increases the angle.he angle.

2. Adduction2. Adduction and and abductionabductionThe movements are perfomed in the sagittal axis.The movements are perfomed in the sagittal axis.The The adductionadduction means the movement of a bone to means the movement of a bone to

ward the midline of the body.ward the midline of the body.The The abductionabduction means the movement of a part aw means the movement of a part aw

ay from the midline of the body.ay from the midline of the body.

3. 3. Rotation Rotation It means moving a bone around its vertical axis.It means moving a bone around its vertical axis.It includes It includes medial rotationmedial rotation and and lateral rotationlateral rotation..PronationPronation and and supinationsupination::The movements are specially for the forearm.The movements are specially for the forearm.The The pronationpronation is a movement of the forearm in which the is a movement of the forearm in which the

palm of the hand is turned backward.palm of the hand is turned backward.The The supinationsupination is the movement in which the palm is tur is the movement in which the palm is tur

ned forward. ned forward. 4. 4. CircumductionCircumductionIt is a movement in which the distal end of a bone moves It is a movement in which the distal end of a bone moves

in a circle while the position of proximal end remains in a circle while the position of proximal end remains relatively stable.relatively stable.

ⅣⅣ) The types of Synovial Joints) The types of Synovial Joints

They can be classified according to the nuThey can be classified according to the number of bones, the axis and the type of movemmber of bones, the axis and the type of movement or the shape of articular surface etc. ent or the shape of articular surface etc.

1. The uniaxial joints 1. The uniaxial joints They permit movement only in one axis (coronal,They permit movement only in one axis (coronal,sagittal or vertical).sagittal or vertical).1) The 1) The hinge jointshinge joints (or trochlear joints) (or trochlear joints)They permit flexion and extension, e.g., theThey permit flexion and extension, e.g., theinterphalangeal joints.interphalangeal joints.2) The 2) The pivot jointspivot jointsThey allow rotation around a long axis, e.g., theThey allow rotation around a long axis, e.g., theproximal radioulnar joint permits rotation of the proximal radioulnar joint permits rotation of the

head of radius.head of radius.

2. The biaxial joints 2. The biaxial joints

They allow movement in two axes which meet at right anglThey allow movement in two axes which meet at right angle to each other.e to each other.

1) The 1) The ellipsoid jointsellipsoid joints (or condyloid joints) They permit fl (or condyloid joints) They permit flexion and extension, adduction and abduction, as well as ciexion and extension, adduction and abduction, as well as circumduction. Their articular surfaces are ellipsoidal or ovarcumduction. Their articular surfaces are ellipsoidal or oval in shape, e.g., the radiocarpal joint.l in shape, e.g., the radiocarpal joint.

2) The 2) The saddle jointssaddle joints Their articular surfaces are concave and convex, opposite tTheir articular surfaces are concave and convex, opposite t

o each other.o each other. They allow movement of flexion, extention, adduction, abThey allow movement of flexion, extention, adduction, ab

duction and circumduction. The carpometacarpal joint of tduction and circumduction. The carpometacarpal joint of the thumb is a good example.he thumb is a good example.

3. The multiaxial joints 3. The multiaxial joints

1) The 1) The plane jointsplane joints (or gliding joint) (or gliding joint) Some of these joints are referred to the multiaxial joinSome of these joints are referred to the multiaxial join

ts. But they permit only a little of movement, e.g., the ts. But they permit only a little of movement, e.g., the acromioclavicular joint.acromioclavicular joint.

2) The 2) The ball and socket jointsball and socket joints They are the most freely moving synovial joints.They are the most freely moving synovial joints. Universal movements are permitted (i.e., in an almost Universal movements are permitted (i.e., in an almost

infinite number of axes), such as flexion and extensioinfinite number of axes), such as flexion and extension, adduction and abduction, medial and lateral rotation, adduction and abduction, medial and lateral rotation, and circumductiom, for example, the shoulder and n, and circumductiom, for example, the shoulder and hip joints. hip joints.