Week 4-Joint Structure and Function PDF

Week 4- Joint Structure and Function Sivapriya Ramakrishnan., MPT, FHEA(UK) Objectives Define joint Enumerate the Principles of joint design List the types of connective tissues. Describe the structure and elements of the connective tissues  Classify the typ...

Week 4- Joint Structure and Function Sivapriya Ramakrishnan., MPT, FHEA(UK) Objectives Define joint Enumerate the Principles of joint design List the types of connective tissues. Describe the structure and elements of the connective tissues  Classify the types of joints  Explain the structure of joint and their function  Differentiate between the open and closed kinematic chains  Describe about the joint positions  Enumerate the Arthrokinematics and Osteokinematics 1.Understand the Implications of Load deformation/stress- strain curve in specific connective tissues 2.Describe the effects of aging, immobilization and injury on connective tissues 2  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 Interfibrillar Proteoglycans Extracellular component component Aggrecan Biglycan Glycoproteins Fibrillar Dicorin Fibronectin 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 Compositio n 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  Synchondrosi joints s  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 Type of joint that resembles like a ring and the other a door hinge component is shaped so that Eg. Inter-phalangeal joints of the it can rotate in 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. Load – Deformation & Stress Strain Curves These curves are used to determine the strength of building materials including human building materials such as bone, ligaments, tendons, joint capsules and other structures that constitute and support human joints In this curve the applied load(external force) is plotted against the deformation Provides information regarding the strength properties of a particular material or structure Load – deformation curve can be transformed into a stress-strain curve by dividing the force by the tissue cross sectional area and the change in length (deformation) by original length Stress = force/cross sectional area Strain = length increase/ original length  Stress – Strain curve in which stress is expressed in load per unit area and strain is expressed in deformation per unit length is used to compare the strength properties of one material with another material  Load – deformation provides information about the elasticity, plasticity, ultimate strength and stiffness of the material as well as the amount of energy the material can store before failure Elastic region In this region deformation of the material will not be permanent and the structure will return to its original dimensions after the removal of the load Yield Point Indicates that at this point the material will no longer react elastically and some deformation will be evident after release of a load. It Signifies the end of elastic region or elastic limit Plastic region Deformation of the material will be permanent when the load is removed If loading continues in the plastic range the material will continue to deform until it reaches the ultimate failure point The total deformation material can sustain before failure is shown by the maximum X- axis value The strength of the material is indicated by the maximum load it can sustain before it reaches the failure point (maximum Y-axis value) The material strength in terms of the energy it can store is indicated by the area under the curve The stiffness of the material (resistance to deformation) is indicated by the slope of the curve Young’s Modulus Young’s modulus, or Modulus of elasticity defines the mechanical behavior of the material It is a measure of the material’s stiffness (resistance offered by the material to external loads) Modulus of elasticity of a material under compressive or tensile loading is represented by the slope of the curve A value for stiffness can be found by dividing the load by the deformation at any point in the elastic range Modulus = Stress (load) Strain (deformation) Young’s Modulus = F/A L /L0 When the first portion of the curve is a straight line the deformation is directly proportional to the materials ability to resist the load If the slope of the curve is steep and modulus of elasticity is high the material will exhibit a high degree of stiffness If the slope of the curve is gradual and the modulus of elasticity is low material will exhibit a low degree of stiffness Mechanical Properties of different connective tissues The strongest materials in human body are the cortical bone, followed by tendons and ligaments The wide range in properties is due to differences in structure and constituents Bone Cortical bone is ‘stiffer’ than cancellous bone Can withstand greater stress Longitudinal sections of bone are stronger than transverse sections Bones can withstand greater compressive stresses than tensile stresses Response of bone to loading is hypertrophy Tendons When subjected to loading, tendons exhibit creep. When stretched, failure occurs due to intrafibrillar slippage interfibrillar slippage disruption of collagen fibers Tendons are able to resist more tensile stresses as compared to compressive and shear forces The larger the tendon, more is the force it can withstand Myotendinous junction is the common site for injury or strain; enthesis is the common site for degeneration 40 Cartilage When a compressive load is applied to cartilage, its volume changes, leading to change in pressure, causing a flow of interstitial fluid Frictional drag is created by flow of fluid through extracellular matrix Ability to resist shear forces depends on amount of collagen Each type of material has its own unique curve, but a typical curve for tendons and extremity ligaments using a constant rate of loading is seen in the diagram Load/deformation curve for a collagenous material Toe region- from O-A Described as the region where in wavy pattern (crimp) that exists in collagen fibers is straightened out In this region the minimal amount of force produces a relatively large amount of deformation (elongation) Toe region may be equated to the area in which an evaluator tests the integrity of a ligament by application of a tensile force This region also represents the slack in a tendon that must be taken up by the muscle before the muscle can apply a force to the bone through the tendon Linear [A-B region] Is the elastic region in which elongation (strain) has a more or less linear relationship with the stress Stiffness or resistance increases in this region so more force is required to produce elongation Each additional unit of applied force creates an equal stress and strain in the tissue In this region of the curve the collagen fibrils are being elongated and are resisting the applied force However with in this region the ligament or tendon returns to its pre stressed dimensions following the removal of a load although because of the viscoelasticity of the structures, the return is time dependent This region illustrates stress and strain that occur during the lower and upper limits of normal physiologic motion and typically extends to about 4% strain B-C region (plastic range) Progressive failure of collagen fibers occurs and the ligament or tendon is no longer capable of returning to its original length Plasticity may be considered as a form of microfailure Recovery from this level of loading will require considerable time because it involves aspects of healing, synthesis of new tissue and cross linking of collagen molecules As the plastic range is exceeded and force continues to be applied, the remaining collagen fibrils rapidly experience increased stress and fail sequentially creating overt failure or macro failure Failure of Connective Tissues In case of a ligament or tendon the failure may occur in the middle of the structures through tearing and disruption of the connective tissue fibers –rupture If failure occurs through a tearing off of the bony attachment of the tendon it is called as avulsion When failure occurs in bony tissue it is called as fracture. Each type of connective tissue is able to undergo a different percentage of deformation before failure Generally , ligaments are able to deform more than cartilage and cartilage is able to deform more than bone However the total deformation also will depend on the size (length, width, or depth) of the structure Mechanical properties vary across tissues and structures due to material and geometry differences Effect of disease, injury & immobilization on joint structures Each structure of human joint has one or more specific functions that are essential for the overall performance of the joint Any process that disrupts any one of the parts of a joint will disrupt the total function of the joint Disease process involving any structure of the joint can lead to deleterious effects on remaining structures also Injury to one structure can cause abnormal stress on unaffected structures and further cause more harm Chapter-Joint Structure and Function  We are good to go Next week Quiz: Week 1- 4