Functional Anatomy Lecture 3. The Articular system.

Functional Anatomy

Lecture 3

The Articular system

• Joints functions:- a connection between two bones.- allow motion- help to bear the weight of the body- provide stability

A joint that allows a great deal of motion will provide very little stability shoulder joint!!!

Conversely, a joint that is quite stable tends to have little motion sternoclavicular joint.

There is often more than one term that can be used to describe the same joint. These terms tend to describe either the structure or amount of motion allowed.

• Types of joints:- fibrous joint - cartilaginous joint- A synovial joint

Fibrous joint

• A fibrous joint has a thin layer of fibrous periosteum between the two bones, as in the sutures of the skull.

Fibrous joints types: Synarthrosis Syndesmosis Gomphosis.

(1) Synarthrosis:

- a thin layer of fibrous between the two bones - No motion between the bones.- The purpose of this type of joint is to provide shape and

strength

(2) Syndesmosis: ‘’Ligamentous joint’’. There is a great deal of fibrous tissue, such as

ligaments and interosseous membranes, holding the joint together.

A small amount of twisting or stretching movement can occur in this type of joint.

e.g. : distal tibiofibular joint distal radioulnar joint.

• ( 3) Gomphosis “bolting together.” This joint occurs between a tooth and the wall of

its dental socket in the mandible and maxilla.

cartilaginous joint (amphiarthrodial joints )

• Hyaline cartilage or fibrocartilage between the two bones.

• e.g.: -fibrocartilage …Disc in the vertebral

-The 1st sternocostal joint.• Allow a small amount of motion,

such as bending or twisting, and some compression.

• These joints provide a great deal of stability.

A synovial joint (Diarthrodial joint )

• A synovial joint has no direct union between the bone ends.

• Diarthrodial joint …….. allows free motion….. not stable.

Synovial Joint structure

- Bone- Ligaments- Capsule- Burse- Tendon

Ligaments (capsular ligaments)• Ligaments are bands of fibrous connective tissue.

• Ligaments functions:- Support and held the two bones of a joint together- Provide attachment for cartilage, fascia, or, in some

cases, muscle. - Joint protection

• Ligaments are flexible but not elastic

Flexibility allow joint motionNonelasticity keep the bones in close

approximation to each other and to provide some protection to the joint.

Ligaments prevent excessive joint movement.

Joint Capsule surrounds and encases the joint and protects

the articular surfaces of the bones. In the shoulder joint, the capsule completely

encases the joint, forming a partial vacuum that helps hold the head of the humerus against the glenoid fossa. In other joints, the capsule may not be as complete.

* There are two layers to the capsule :The outer layerThe inner layer

• The outer layer of the capsule is made up of a strong fibrous tissue that holds the joint together and provides support and protection to the joint. This fibrous layer is usually reinforced by ligaments.

• The inner layer is lined with a synovial membrane, which is a thick, vascular connective tissue that secretes synovial fluid.

Synovial fluid is a thick, clear fluid, much

like the white of an egg that lubricates the articular cartilage. This substance reduces friction and helps to keep the joint moving freely. It provides some shock absorption and is the major source of nutrition for articular cartilage.

Cartilage

• Cartilage is a dense fibrous connective tissue capable of withstanding a great amount of pressure and tension.

• Cartilage types:- Hyaline cartilage- fibrocartilage- Elastic cartilage.

Hyaline cartilage(Articular cartilage)

• Hyaline cartilage covers the ends of opposing bones

• Hyaline cartilage + Synovial fluid it provides a smooth articulating surface in all synovial joints.

• Hyaline cartilage has no blood or nerve supply of its own and must get its nutrition from the synovial fluid. Therefore, when it is damaged it is unable to repair itself

• The articular surface is very smooth and covered with cartilage called hyaline or articular cartilage.

Fibrocartilage• Fibrocartilage a shock absorber in weight-

bearing joints. E.g.:• Knee joint menisci (semilunar-shaped

cartilage) tibia.

• Vertebral bones intervertebral discs are capable of absorbing an amazing amount of shock that is transmitted upward from weight-bearing forces.

• Fibrocartilaginous disk between the clavicle and sternum.. Functions?!!!

• Fibrocartilaginous disk between the clavicle and sternum (1) absorbing the shock transmitted along the clavicle to the sternum should you fall on your outstretched hand.

(2) This disk helps prevent dislocation of the sternoclavicular joint.

(3) It is also important in allowing motion The disk, which is attached to the sternum at one end and the clavicle at the other, is much like a swinging door hinge that allows motion in both directions. This double-hung hinge allows the clavicle to move on the sternum as the acromial end is elevated and depressed. In effect, the fibrocartilage divides the joint into two cavities, allowing two sets of motion.

The shoulder fibrocartilage labrum deepens the shallow glenoid fossa, making it more of a socket to hold the humeral head.

• Wrist joint Triangular Fibrocartilage disk fills the gap between two bones the ulna does not extend all the way to the carpal bones as does the radius. In this gap there is located a small triangular disk that acts as a space filler and allows force to be exerted on the ulna and carpals without causing damage.

Elastic cartilage

• It is designed to help maintain the shape of a structure.

• E.g.: The external ear Eustachian tube.

The larynx, where its motion is important to speech.

Muscles provide the contractile force that causes joints to move. They must, therefore, span the joint to have an effect on that joint. Muscles are soft and cannot attach directly to the bone.

Tendon • A tendon connect to bone. The tendon may be- A cylindrical cord long head of the biceps

tendon

• A flattened band The rotator cuff

• A Tendon sheath The tendons passing over the wrist all have tendon sheaths (Why??)

- An aponeurosis Latissimus dorsi muscle, Anterior abdominal muscle (linea alba.)

Bursae• Small padlike sacs.• Bursae are located in areas of excessive friction,

such as under tendons and over bony prominences. • These sacs are lined with synovial membrane and

filled with a clear fluid.

• Their purpose is to reduce friction between moving parts

For example,subdeltoid bursa in the shoulder the deltoid

muscle passes directly over the acromion process Repeated motion would cause excessive wearing of the muscle tissue prevents excessive friction and reduces the likelihood of damage.

• Bursa types: - Natural bursa and acquired bursa. It is possible to

develop a bursa in an area that normally does not have excessive friction if, for some reason, this area has become the site of excessive friction. These acquired bursae tend to occur in places other than joints.

- For example, a person may develop a bursa on the lateral side of the third finger of the writing hand. This is often called the “student’s bursa” because students often do a lot of writing and note taking.

These bursae disappear when the activity is stopped or greatly reduced.

synovial joint motions

The amount of motion allowed at each joint and the direction of that motion are dictated by the shape of the bone ends and by the articular surface of each bone.

Shoulder joint has a great deal of motion in all direction!!!!

The knee has a great deal of motion but in a specific direction!!!!

synovial joint motions

• The two muscle attachments across a joint are:– Origin attachment to the immovable bone.– Insertion attachment to the movable bone Described as movement along transverse

(horizontal), frontal, or sagittal planes

synovial joint motions

• Synovial/Diarthrodial Joints further classified by number of axes, shape of joint and type of motion allowed (Degree of freedom).

Basic types of dynamic motion

• Linear motion (gliding)• Angular motion• Rotation

Linear Motion

• One flat bone surface glides or slips over another similar surface

E.g.: - intercarpal joint - intertarsal joints

Initial position Gliding movement

Pencil at right angle to the surface

Pencil remains vertical , but changes position

Angular Motion• Pencil maintains position, but changes

orientation– Tip stays fixed; pencil does not rotate

E.g.: - Flexion/ Extension - DF/PF- Abd/Add

Circumduction????!!!

Angular Motion: Circumduction

• Angular motion in a circle Again, tip does not rotate!!!

Rotation motion

• NOT angular !!!!!

Pencil maintains position and orientation, but spins.

E.g.: shaking your head

With tip at same point, the angle of the shaft remains unchanged as the shaft spins around its longitudinal axis

Terminology

Concave : hollowed or rounded inward.

Convex : curved or rounded outward.

Congruent: The surfaces of the joint are equal.

Incongruent : The surfaces of the joint are not equal

All joint surfaces are either ovoid or sellar (Saddle).

• An ovoid joint has two bones forming a convex-concave relationship.

For example, in the MCP joint, one surface is concave (proximal phalanx) and the other is convex (metacarpal).

Most synovial joints are ovoid.

Usually in an ovoid joint, one bone end is larger

than its adjacent bone end This permits a greater ROM on a less articular surface, which reduces the size of the joint.

• In a sellar or saddle-shaped joint: each joint surface is concave in one direction and

convex in another.

• it is concave in a front-to-back direction and convex in a side-to-side direction.

e.g.: The carpometacarpal (CMP) joint of the thumb

Synovial Joints classifications Axes of rotation:

Nonaxial joint

Uniaxial joint (Monaxial joint)

Biaxial joint Triaxial joint (multiaxial joint )

Anatomical (Shape) Gliding ( plane) joint Hinge joint Pivot joint Condyloid joint Saddle joint Ellipsoid joint Ball and socket

Degree of freedomOne DF. Two DF. Three DF.

Non-axial joint

• In a nonaxial joint ….. linear movement!!!!!!• The joint surfaces are relatively flat and glide

over one another instead of one moving around the other.

• E.g. : carpal bones

• Unlike most other types of diarthrodial joint motion, nonaxial motion occurs secondarily to other motion !!!!!!!!!!!!

• E.g.: Elbow joint… can be flexed and extend without

moving other joints

carpal bones cannot be moved by themselves. (Motion of the carpals occurs when the wrist

joint moves in either flexion and extension or abduction and adduction)

Carpal motions.3gp

Other Examples!!!!!• Acromioclavicular joint • Sternoclavicular joint • Vertebrocostal joints• Sacroiliac joint

Plane Joint

Nonaxial Joint

Various DF

Gliding movement

A uniaxial joint• angular motion occurring in one plane around

one axis.

Hinge Joint (Ginglymus) • Convex surface of one bones

fits into concave surface of 2nd bone

• E.g.: elbow……. the convex shape of the humerus fitting into the concave shaped ulna.

Motion: sagittal plane frontal axis flexion and extension

Other Examples!!!!!

Interphalangeal joints: DIP/ PIP/ IP

Hinge /Interphalangeal joints DIP/PIP

Knee

Knee Joint Motion: sagittal plane frontal axis flexion and

extensionKnee joint …uniaxial joint

• Therefore The knee is a modified hinge joint…. a uniaxial joint…. because it has active motion only around one axis.

Hinge Joint

Uniaxial Joint

One DF

Flexion/Extension movement

Pivot Joint• Rounded end of one bone

protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another

• Only uniaxial movement allowed

Examples!!!!

• Radioulnar joint pivot jointTransverse plane Longitudinal axisUniaxial motion

Another Example!!!!

• The motion of the atlantoaxial joint of C1 and C2 is also pivot motion.

Pivot Joint

Uniaxial Joint

One DF

Rotation movement

Biaxial joint motion

Oval articular surface of one bone fits into a complementary depression in another–Both articular surfaces are

oval–Biaxial joints permit all

angular motions

Examples!!!! Condyloid (Ellipsoid) joint

• Wrist jointSagittal plane Frontal axis Flex/ExtFrontal plane Sagittal axis Radial/ulnar deviation• Metacarpophalangeal (MCP) joints (knuckles)

Condyloid Joint

Biaxial Joint

Two DF

Flexion/extension, Abd/Add

Saddle Joint • Biaxial Joint• Each articular surface has both concave and

convex areas

Example!!!carpometacarpal (CMC) joint of the thumb:• Trapezium concave in a front-to-back direction and convex in a

side-to-side direction • first metacarpal bone the opposite shape.

• The thumb is the exception because flexion/extension and abduction/adduction do not occur in these traditional planes.

Why ???!!!! Due to the distinct shape of this joint!!!

Saddle shape flexion / extension

abduction / adduction CircumductionRetropulsionOpposition

Saddle Joint

Biaxial Joint

Two DF

Flexion/extension, Abd/Add

Triaxial joint (multiaxial joint)Ball-and-socket joint

A spherical or hemispherical head of one bone articulates with a cuplike socket of another

Multiaxial joints permit the most freely moving synovial joints allow motion in: The Sagittal plane frontal axis flexion and extensionThe Frontal plane sagittal axis Abd/ AddThe Transverse plane vertical axis rotation

Examples!!!

The Shoulder joint The Hip joint

Ball and socket Joint

Triaxial Joint

Three DF

Flx /ext, Abd /Add, Rotation

Arthrokinematics

• OSTEOKINEMATIC to name the movements that occur between bones at synovial joints. These terms describe the movements that occur around a center of rotation, namely the joint axis.

–flexion / extension–abduction / adduction– internal rotation / external rotation

End feel

• End feel is a subjective assessment of the quality of the feel when slight pressure is applied at the end of the joint’s passive range of motion.

• It was first described by Cyriax (1983). He stressed the importance of how the “end feel” felt to the examiner’s hands during passive motion.

• The three major types of end feel are:

Bony end feel Capsular end feel Empty end feel Springy block end feelSoft tissue end feel Muscular end feel

Bony (Hard) end feel

• motion is stopped when bone contacts bone Normal end for some joints. Abnormal if there are loose fragments in joint that stop the motion.

e.g.: normal terminal elbow extension..

Capsular (soft) end feel• motion is stopped by soft tissues being

compressed.

Normal for some joints. Abnormal if there is a boggy feel to motion, indication of edema

e.g.: This occurs in full normal joint motion of the shoulder and is related to capsular restriction

Empty end feel

• motion is stopped in response to the patients request (experiencing considerable pain) …. complete disruption of soft-tissue constraints

always abnormal

Springy block (Firm) end feel

• motion is stopped by soft tissue that have reached there limit of stretch.

If motion is limited this is a sign of tissue shortening

A rebound movement felt at the end of the ROM characterizes springy block. This occurs with internal derangement of a joint, such as torn cartilage.

Soft tissue end feel

• Asymptomatic limited ROM characterizes soft tissue approximation.

• This occurs when the soft tissue of body segments prevents further motion

e.g.: at normal terminal elbow flexion

Muscular end feel

• Muscle guarding is a reflex muscle spasm during motion.

• It is a protective response seen with acute injury. Palpation of the muscle will reveal the muscle in spasm

• The ability to palpate normal end feel and to distinguish changes from normal end feel is important in protecting joints during ROM exercises.

ARTHROKINEMATICS

• Arthrokinematics is the general term for the specific movements of joint surfaces.

• Arthrokinematics movements taking place within the joint at the joint surfaces.

• We cannot see the movement & Not under voluntary control Joint Play / Accessory motion!!!

• Arthrokinematic motion types: Roll Glide (Slide) Spin

Roll• Roll is the rolling of one joint surface on

another. New points on each surface come into contact throughout the motion.

• Example:ball rolling across the ground.

Glide

• Glide, or slide, is linear movement of a joint surface parallel to the plane of the adjoining joint surface. In other words, one point on a joint surface contacts new points on the adjacent surface.

• Example:An ice skater’s skate blade

Spin• Spin is the rotation of the movable joint

surface on the fixed adjacent surface. Essentially the same point on each surface remains in contact with each other.

Examples: • Humerus rotating medially & laterally in the glenoid fossa.• The head of the radius spinning on the capitulum of the humerus.

• Most joint movement involves a combination of all three of these motions.

• Examples:

Roll and slide Shoulder joint Abduction !!!!

Roll and slide and spin Knee joint Home screw mechanism & patella gliding!!!!

Roll and slide and spin

Normal joint surface movement is necessary to ensure long-term joint integrity

Why to study Arthrokinematics???

Rules of concavity and convexity• Movements at joint surfaces (arthrokinematics)

follow the rules of concavity and convexity.

• Each joint or articulation involves two bony surfaces, one that is convex and one that is concave……

• If the moving joint surface is CONVEX, sliding is in the OPPOSITE direction of the angular movement of the bone.

• If the moving joint surface is CONCAVE, sliding is in the SAME direction as the angular movement of the bone.

Convex-concave law

Example: Glenohumeral articulation Glenoid fossa concave surface

with Humeral head convex surface !!!

Convex –concave law???

CONVEX OPPOSITE direction

CONCAVE SAME direction

Joint surface positions

congruency • closed-pack position

incongruent •open-packed position

Congruent Joint (closed-pack position )

In this position:

(1) The maximum area of surface contact occurs

(2) the attachments of the ligaments are farthest apart and under tension

(3) capsular structures are taut

(4) the joint is mechanically compressed and difficult to distract

• Examples:- patellofemoral joint: Knee in the fully extended

position manually move the patella slightly from side to side and up and down.

Knee flexion patellar movement is not possible.

Close-packed position of the patellofemoral joint is knee flexion.

- Knee Full extension & lateral rotation of tibia- Glenohumeral Abd & lateral rotation- Elbow full Extension- Wrist Extension with ulnar deviation- Hip Full extension & medial rotation- Ankle Maximum dorsiflexion

By the nature of the characteristics of a close-packed position, a joint usually is injured when in this position.

For example, a knee joint that sustains a lateral force when it is extended (closed packed position) is much more likely to be injured than when it is in a flexed or semi-flexed position (loose packed position).

When a joint is swollen, it cannot be moved into the close-packed position.

Incongruent Joint (open-pack position )

In all other positions the joint surfaces are incongruent.

The position of maximum incongruency is called the open-packed or loose-packed position (resting position).

Parts of the capsule and supporting ligaments are lax.

Because the ligaments and capsular structures tend to be more relaxed, joint mobilization techniques are best applied in the open-packed position.

It is these open-packed positions that allow for the roll, spin, and glide, necessary for normal joint motion….. Accessory motion

Thank you

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