Week 4-Joint PDF - Anatomy Notes

INTRODUCTION ▪ A joint (articulation)is used to connect one component of a structure with one or more other components. ▪ Functions of joints- mobility, stability, dynamic. Principles of joint Design 1. Joints that serve a single function are less complex than...

INTRODUCTION ▪ A joint (articulation)is used to connect one component of a structure with one or more other components. ▪ Functions of joints- mobility, stability, dynamic. Principles of joint Design 1. Joints that serve a single function are less complex than joints that serve multiple functions 2. The design of a joint is determined by its function and the nature of its components Structure of joints ▪ Joints are made up of connective tissues like bursae, bones, ligaments, tendons, menisci etc. ▪ The structure of the connective tissues are extremely varied and biomechanical compositions as well. Connective tissue Cellular components Extracellular components  Resident cells Circulating Cells Cellular component Chondroblasts Lymphocytes Fibroblasts Macrophages Osteoblasts Tenocytes Proteoglycans Extracellular Interfibrillar component component Aggrecan Biglycan Glycoproteins Dicorin Fibronectin Fibrillar component Perlecan Fibromodulin Versican Thrombosporin Collagen & Elastin Link protein Ligaments ▪ Connective tissue structure that connect or bind one bone to another either at or near a joint ▪ Often appear as dense white bands or cords of connective tissue ▪ Named according to their location, shape(anterior longitudinal ligament),bony attachments(coraco humeral ligament) and relationship to one another(radio ulnar ligament) or person who identified it (Y ligament of Bigelow). ▪ Ligaments are heterogenous structures composed of small amount of cells and large amount of extra cellular matrix Composition 1. Cellular component – fibroblasts 2. Extra cellular matrix- a.Interfibrillar component- PGs & glycoproteins b.Fibrillar component-collagen  elastin ▪ Ligamentum nuchae and ligamentum flavum have more elastin than collagen. ▪ Enthesis-ligamentous bony insertion site Tendons ▪ Connect muscle to bone ▪ Composed of small cellular component and a large extracellular matrix Cellular component – fibroblasts Extracellular matrix a.Interfibrillar component- water, PGs & GAG compounds b.Fibrillar component- varying proportions of collagen & elastin ▪ Collagen fibrils are composed of micro fibrils grouped together to form primary bundles known as fibers ▪ Groups of fiber bundles enclosed by a loose connective tissue are called endotendon ▪ Endotendon containing types I &II collagen also encloses nerves, lymphatics and blood vessels supplying the tendon to form a secondary bundle called as Fascicle Tendon ▪ Sheath that covers all secondary bundles is called as Epitenon ▪ Double layered sheath of areolar tissue that is loosely attached to the outer surface of epitenon is called as peritenon or paratenon ▪ Connective tissue at the bony ends of the tendon changes first to un mineralized fibro cartilage and then to mineralized fibro cartilage and finally to the bone ▪ Myotendinous junction – attachment of tendon to muscle is formed as collagen fibers in tendons merge with actin filaments in the muscle’s sarcomeres 9 Bursae ▪ Flat sacs of synovial membrane in which inner sides are separated by a fluid film ▪ Located where moving structures are in tight approximation ▪ Seen between tendon and bone, bone and skin, muscle and bone or ligament and bone 1. Subcutaneous bursae 2. Subtendinous bursae 3. Submuscular bursae 10 White fibrocartilage Cartilage forms bonding cement in joints that permit little motion found in inter vertebral disks,glenoid and acetabular labra consists of type I collagen Yellow elastic fibrocartilage found in ears and epiglottis has higher ratio of elastin to collagen fibers Hyaline articular cartilage It is the articular cartilage forms a thin covering on the ends of the bones in the joints provides a smooth, resilient,low friction surface for joint articulation these surfaces are capable of bearing and distributing weight over a persons life time. Composition of cartilage Cellular component – chondrocytes, Chondroblasts Extra cellular matrix a. Interfibrillar component- water, PGs & noncollagen PGs/GAG (chondroitin sulfate & keratan sulfate) ratio varies higher the chondroitin sulfate concentration the better the tissues resistance to compressive forces keratan sulfate concentration increases in aging and in joints with arthritic changes and decreases in immobilization if proportion of keratan sulfate exceeds the chondroitin sulfate proportion the ability of the cartilage to bear loads is compromised b. Fibrillar component- varying proportions of collagen(II main) & elastin 12 Bone Hardest of all connective tissues Cellular component – fibroblasts, fibrocytes, osteoblasts, osteocytes, osteoclasts and osteoprogenitor cells Extra cellular matrix- a. Interfibrillar component- minerals, water, PGs & glycoproteins b. Fibrillar component- reticular fibers, collagen (I) & elastin 13 Joint Types and Kinematic Chain 14 Major classification of joints Joints (Arthroses or articulations) can be classified into two broad categories on the basis of type of materials and the methods used to unite the bony components Synarthroses (non synovial joints)- Immovable Diarthroses (synovial joints)-Movable Amphiarthroses- Slighlty movable Subdivisions of joint categories are based on materials used, the shape and contours of the articulating surfaces and the type of motion allowed. 15  Synarthroses Sutures Fibrous Gomphoses joints Syndesmosis Cartilaginous joints ▪ Symphysis Cartilaginous ▪ Synchondrosis joints  Synarthroses Interosseus connective tissue connects the bony components Two types - Fibrous & Cartilaginous Fibrous Joints- Fibrous tissue directly unites bone to bone Sutures: Two bony components are united by a collagenous sutural ligament or membrane Allows some movement early stages Eg: skull Fusion of the two opposing bones in suture joints occurs later in life and leads to the formation of a bony union- Synostosis. b) Gomphosis Surfaces of bone components are adapted to each other like a peg in a hole and connected by a fibrous tissue Eg: tooth &mandible/maxilla c) Syndesmosis Two bony components are joined directly by an interosseus ligament, a fibrous cord or aponeurotic membrane. Allows some amount of motion. Eg: shaft of tibia & fibula. B. Cartilaginous Joints Materials used to connect the bony components are either fibrous cartilage or hyaline cartilage a. Symphyses: Bony components are covered with a thin lamina of hyaline cartilage and directly joined by fibro cartilage in the form of disks or pads Eg: symphysis pubis, intervertebral joints. b. Synchondrosis: Material used for connecting the two components is hyaline cartilage Eg: first chondrosternal joint. Diarthroses The bony components are indirectly connected to one another by means of a joint capsule that encloses the joint Features: Joint capsule Joint cavity Synovial membrane Synovial fluid Hyaline cartilage Can be divided into three types on the basis of number of axes about which gross visible movement occurs  Biaxial a. Condyloid b. saddle Triaxial a. Plane b. Synovial Uniaxial a. Hinge b. Pivot  Uniaxial Joint Motion is allowed in only one of the planes and around one axis. They are described as having 1of freedom of movement Pivot joints Hinge joints One component is shaped like a Type of joint that resembles ring and the other component is a door hinge shaped so that it can rotate in Eg. Inter-phalangeal joints of the the ring fingers Eg. Atlanto-axial joint  Biaxial Joint The bony components are free to move in two planes and around two axes. Therefore these joints have 2° of freedom. Condyloid - Joint surfaces are Saddle-Joint in which each surface shaped so that the concave surface is both convex in one plane and of one bony component is allowed to concave in another plane slide over the convex surface of In this type of joint, each bone is another in 2 directions. saddle-shaped and fits into E.g. MCP joint. Convex distal end of complementary regions of the MC bone and the concave other & variety of movements are proximal end of the proximal possible phalanx form it E.g. CMC joint of thumb.  Triaxial Joint Also called as multi axial diarthrodial joints. They are free to move in 3 planes around 3 axes & they have 3° of freedom Motions at these joints can also occur in oblique planes Plane-Have a variety of surface Ball and socket-Formed by ball like configurations Permit gliding convex surface been fitted into a between 2 or more bones E.g. carpal joints. concave socket E.g. Hip joint: Joint Function 1 2 Synarthrodial joints - relatively Diarthrodial joints – complex simple in design and function in design and are designed for primarily as stability joints mobility all though they though permit slight amount of provide some amount of mobility stability  Kinematic Chain The system of joints and links is constructed so the motion of one joint will produce motion at all of the other joints in the system in a predictable manner Joints of human body are linked together to form a series in such a way that motion at 1 joint is accompanied by motion at an adjacent joint one joint can move independently of others in Open the chain. When one end of the chain remains fixed, it creates a closed system or closed kinematic chain-under these circumstances, movement at one joint chain automatically creates movements in Closed other joints in the chain.  These engineering terms have been applied to human movements primarily to describe movements that take place under weight-bearing and NWB. Because the joints of the human body are linked together, motion at one of the joints in the series is, under weight-bearing conditions, accompanied by motion at one or more other joints. When a person stands in a erect position, bends both knees there is simultaneous motion at the ankle and hip However, when the leg is lifted from the ground the knee is free to bend without causing motion at the hip or the ankle  Closed Kinematic Chain ▪ Movement of one joint causes movement of other joint in the link in a limited and predictable manner ▪ Movement behaviors in weight bearing and weight shifting ▪ These are the complex reactions of the entire body when upper and lower extremities ground through the floor ▪ The joints of the lower limb and the pelvis function as a closed kinematic chain when a person is standing on both legs ▪ The end of the limbs are fixed to the ground and the upper ends are fixed to the pelvis. This is an example of closed kinematic chain  Open Kinematic Chain ▪ Movement behavior in free space ▪ Here the arms and legs move about open space on the foundation of the trunk ▪ Distal segments are free to move while proximal segments can remain stationary ▪ When the ends of the limbs are free to move the system is referred to as open kinematic chain ▪ Flexion and extension of the knee during unilateral stance ▪ Equipment examples include Cybex, manual muscle testing Therapeutic Implication Joints are interdependent Although the joints in the human body do not always behave in an entirely predictable manner in either a closed or an open chain, the joints are interdependent. A change in the function or structure of one joint in the system will usually cause a change in the function of a joint either immediately adjacent to the affected joint or at a distal joint. For example, if the ROM at the knee were limited, the hip and / or ankle joints would have to compensate in order that the foot could clear the floor when the person was walking, so that he or she could avoid stumbling.