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.

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

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. Fibrocartilage - shock absorber, important in weight bearing joints, like the knee (menisci) and vertebrae (disk). Hyaline (articular) cartilage - no blood supply, once damaged does not repair Amphiar-throdial

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 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. The knee, on the other hand, has a great deal of motion but in a specific direction. In examining the distal end of the femur, you will note that there are two ridges much like the rocker surfaces of a rocking chair. The proximal end of the tibia has two articular surfaces with a high area (intercondylar eminence) in between them. These articular surfaces allow a great deal of motion but, like the rocking chair, in only one direction.

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 When ligaments surround a joint, they are called capsular lignment

Ligaments are flexible but not elastic Flexibility  allow joint motion Nonelasticity  keep the bones in close approximation to each other and to provide some protection to the joint. Ligaments prevent excessive joint movement. Elasticity is the ability to stretch and return to the original shape whilst flexibility is the ability to bend.

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 layer The 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. Hyaline (articular) cartilage - no blood supply, once damaged does not repair

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. The importance of knee menisci should not be underestimated. They have an important function in shock absorption and force distribution across the knee joint by increasing the contact area; the menisci occupies about 70% of the total contact area of the knee joint, which leads to a decrease in the pressure on the medial and lateral compartment (Renström and Johnson, 1990). In meniscectomy, surgical removal of a meniscus, the contact area is decreased to the half and as the force is constant; the amount of pressure per unit area in the knee joint will increase (Fukubayashi and Kurosawa, 1980). As a result, meniscectomy is believed to be a risk factor of knee OA, where patients with partial or total meniscectomy have showed a radiographic knee OA changing.

Vertebral bones  intervertebral discs  are capable of absorbing an amazing amount of shock that is transmitted upward from weight-bearing forces. intervertebral disks…. Because of their very dense structure, these disks 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 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 Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other muscles. Tendons and muscles work together to move bones. Biceps brachii muscle: long head  superaglonid tubericle Short head coracoid process of scapula  radial tubersity

A flattened band  The rotator cuff Rotator cuff muscles: superaspinatus, Infraspinatus, subscapulars, Ters minor.

A Tendon sheath  The tendons passing over the wrist all have tendon sheaths (Why??) These fibrous sleeves surround the tendon when it is subject to pressure or friction, such as when it passes between muscles and bones or through a tunnel between bones. The tendons passing over the wrist all have tendon sheaths. These sheaths are lubricated by fluid secreted from their lining.

An aponeurosis  Latissimus dorsi muscle, Anterior abdominal muscle (linea alba.) Strength!!!! provide a base of muscular attachment where no bone is present but where great strength is needed. meaning 'broadest [muscle] of the back' (Latin latus meaning 'broad', latissimusmeaning 'broadest' and dorsum meaning the back)- Spinous processes of vertebrae T7-L5, thoracolumbar fascia, iliac crest, inferior 3 or 4 ribs and inferior angle of scapula

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. The same arrangement occurs in the elbow where the triceps tendon attaches to the olecranon process. Some joints, such as the knee, have many bursae.

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

Shoulder joint has a great deal of motion in all direction!!!! 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!!!! the distal end of the femur, you will note that there are two ridges much like the rocker surfaces of a rocking chair. The proximal end of the tibia has two articular surfaces with a high area (intercondylar eminence) in between them. These articular surfaces allow a great deal of motion but, like the rocking chair, in only one 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 classical, physiological, or osteokinematic motion…. (ROM). 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. Knowing that a joint surface is concave or convex is important because shape determines motion In a sellar or saddle-shaped joint, each joint surface is concave in one direction and convex in another. The carpometacarpal (CMP) joint of the thumb is perhaps the best example of a sellar joint. If you look at the carpal bone (trapezium), it is concave in a front-to-back direction and convex in a side-to-side direction. The first metacarpal bone that articulates with the carpal bone has just the opposite shape. It is convex in a front-to-back direction and concave in a side-to-side direction. 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 An ovoid joint has two bones forming a convex-concave relationship. For example, in the metacarpophalangeal 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.

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 Joints can also be described by the degrees of freedom, or number of planes, in which they can move. Not a good classification as there are often small but vital movements in other planes (e.g. knee rotation at end of flexing) and cannot take account of sliding movement. 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 freedom One DF. Two DF. Three DF. DF types: Translation – movement along X, Y, and Z axis (three degrees of freedom) Rotation – rotate about X, Y, and Z axis (three degrees of freedom)

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 Linear :'gliding, a movement of bone parallel to the plane of the adjoining bone, all the parts of the bone move the same distance(no rotation about an axis)'

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)

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. The sagittal axis is a point that runs through a joint from front to back. The frontal axis runs through a joint from side to side. The vertical axis, also called the longitudinal axis, runs through a joint from top to bottom. Joint movement occurs around an axis that is always perpendicular to its plane.

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 Ging-lymus The sagittal axis is a point that runs through a joint from front to back. The frontal axis runs through a joint from side to side. The vertical axis, also called the longitudinal axis, runs through a joint from top to bottom. Joint movement occurs around an axis that is always perpendicular to its plane.

Other Examples!!!!! Interphalangeal joints: DIP/ PIP/ IP

Hinge /Interphalangeal joints DIP/PIP

Knee

Knee Joint Motion: sagittal plane  frontal axis  flexion and extension Knee joint …uniaxial joint During the last few degrees of extension…… to lock the knee …. Depends on how is free { closed or open chain} if it’s closed …. the femur rotates medially on the tibia…..(why??) The size of medial

During the last few degrees of extension…… the femur rotates medially on the tibia….. This rotation is not an active motion but the result of certain mechanical features present. Looking at the same spin, or rotational, movement during non–weight-bearing extension (open-chain action), the tibia rotates laterally on the femur. These last few degrees of motion lock the knee in extension, which is sometimes referred to as the screw-home mechanism of the knee. With the knee fully extended, an individual can stand for a long time without using muscles. Therefore The knee is a modified hinge joint…. a uniaxial joint…. because it has active motion only around one axis. The knee must be “unlocked” by the femur rotating laterally on the tibia for knee flexion to occur. It is this small amount of rotation of the femur on the tibia, or vice versa, that keeps the knee from being a true hinge joint. Because this rotation is not an independent motion, it will not be considered a knee motion. During the last few degrees of extension…… the femur rotates medially on the tibia….. This rotation is not an active motion but the result of certain mechanical features present. Looking at the same spin, or rotational, movement during non–weight-bearing extension (open-chain action), the tibia rotates laterally on the femur. These last few degrees of motion lock the knee in extension, which is sometimes referred to as the screw-home mechanism of the knee. With the knee fully extended, an individual can stand for a long time without using muscles. The knee must be “unlocked” by the femur rotating laterally on the tibia for knee flexion to occur. It is this small amount of rotation of the femur on the tibia, or vice versa, that keeps the knee from being a true hinge joint. Because this rotation is not an independent motion, it will not be considered a knee motion.

Flexion/Extension movement 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!!!! The inferior tibiofibular joint is a syndesmosis (fibrous union) between the concave distal tibia and the convex distal fibula. Because it is not a synovial joint, there is no joint capsule. However, there is fibrous tissue separating the bones and several ligaments holding the joint together. Much of the strength of the ankle joint is dependent upon a strong union at this joint. The ligaments holding this joint together allow slight movement to accommodate the motion of the talus The superior tibiofibular joint is the articulation between the head of the fibula and the posterior lateral aspect of the proximal tibia. It is a uniaxial plane joint. Being a synovial joint, it has a joint capsule. Ligaments reinforce the capsule. The gliding motion present is relatively small. It functions to dissipate the torsional stresses applied at the ankle joint. Radioulnar joint pivot jointTransverse plane  Longitudinal axisUniaxial motion Supination and pronation

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 joint Sagittal plane  Frontal axis Flex/Ext Frontal plane Sagittal axis  Radial/ulnar deviation Metacarpophalangeal (MCP) joints (knuckles)

Flexion/extension, Abd/Add 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 carpometacarpal (CMP) joint of the thumb is perhaps the best example of a sellar joint. If you look at the carpal bone (trapezium), it is concave in a front-to-back direction and convex in a side-to-side direction. The first metacarpal bone that articulates with the carpal bone has just the opposite shape. It is convex in a front-to-back direction and concave in a side-to-side direction.

Due to the distinct shape of this joint!!! Saddle 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 Circumduction Retropulsion Opposition the thumb flexion and extension occur in the frontal plane as an inward and outward motion, respectively. Likewise, abduction and adduction of this saddle joint occur not in a sideways motion but in the sagittal plane as a front-to-back motion, with the thumb moving out in front of and back in toward the palm. Circumduction of the CMC joint occurs in both planes. In other words, as the thumb travels through space in a circling motion, it crosses the frontal plane twice and the sagittal plane twice as it completes 360 degrees of movement. Opposition also requires a partial circling motion or arc as the thumb moves inward to make contact with each of the four fingers, and therefore it also occurs in both planes of movement. The only synovial joint in the body with the distinction of being considered a saddle joint is the carpometacarpal (CMC) joint in the thumb. It is located roughly an inch (2.54 cm) above the wrist at the base of the thumb, between the carpal bones and the metacarpal bones. Due to the distinct shape of this joint, it is said to permit movement in two planes — the sagittal, or front-to-back plane, and the frontal, or side-to-side plane. When the hand is in anatomical position &mdahs; that is, when the arm is at the side with the palm facing forward — any movement of the thumb forward and backward would be occurring in the sagittal plane, and any movement outward and inward would be occurring in the frontal plane.

Flexion/extension, Abd/Add 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 extension The Frontal plane sagittal axis  Abd/ Add The Transverse plane vertical axis  rotation

Examples!!! The Shoulder joint The Hip joint

 

Flx /ext, Abd /Add, Rotation 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 feel Soft 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.. Morphology

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 Morphology

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.

Roll Glide (Slide) Spin 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. Humeroradial Joint: - Synovial Joint - Gliding or Plane. - No real “true” movement. – humeroradial joint formed between the spherical capitellum of the humerus, and the concave head of the radius (fovea). Humerradial joint some time is considered as  a limited ball and socket joint / hinge joint !!!!! Why??!!! The humeroradial articulation is not involved in the hinge movement at the elbow, since the ends of the respective bones are scarcely in contact during flexion. The humero-radial articulation is only passively involved in the pivot movement of the proximal radio-ulnar joint, since the radius rotates in the socket about its long axis, and the actual pivot movement takes place in the proximal and distal radio-ulnar articulations.  

Roll and slide     Shoulder joint   Abduction !!!! 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!!!! e.g.: - Roll and slide movement: A tire on a car that is spinning on a sheet of ice

Roll and slide and spin  Also, in these open-packed positions a certain amount of accessory motions, or joint play, can be demonstrated. This is the passive movement of one articular surface over another. Because joint play is not a voluntary movement, it requires relaxed muscles and the external force of a trained practitioner to correctly demonstrate it.

Why to study Arthrokinematics??? Normal joint surface movement is necessary to ensure long-term joint integrity

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……

Convex-concave law 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.

Example: Glenohumeral articulation Glenoid fossa  concave surface with    Humeral head  convex surface !!! Convex –concave law???

CONCAVE   SAME direction CONVEX   OPPOSITE direction MCP joint  Condyloid (Ellipsoid) joint

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 Testing !!!

- patellofemoral joint: 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. When ligaments and capsular structures are tested for stability and integrity, the joint is usually placed in the close-packed position.

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 