Joints are Classified According to Structure and Movement

Chapter 8: Joints Section 1: Joint Structure and Movement 8.1: Joints are classified according to structure and movement Joints or Articulation: Locations where two or more bones meet - Only points at which movements of bones can occur - Joints allow mobility and flexibility while preserving bone strength - Amount of movements allowed is determines by anatomical structure of joint - Other word for joint is Articulation or Arthrosis Categorized By: Range of motion (ROM) is determined by the amount of motion allowed, or structurally, by anatomical organization Arthrology: Is the study of joints Kinesiology: Is the study of motion of the human body (Kinesi=movement) Clinical Talk: “One bone articulates with another bone”; means that the two bone form a joint of some type Functional Classification of Joints Synarthrosis: No movement allowed; extremely strong - Located where movement between bones must be prevented Amphiarthrosis: Little movement allowed (more that Synarthrosis), much stronger than diarthrosis, articulating bones connected by collagen fibers or cartilage Diarthrosis: Freely moveable, all diarthroses are synovial joints Structural Classification of Joints Fibrous Joints: The bones are held together by dense irregular connective tissue that is rich in collagen fibers (NO SYNOVIAL CAVITY) Cartilaginous Joints: The bones are held together by cartilage (NO SYNOVIAL CAVITY) Synovial Joints: The bones forming the joint have a synovial cavity and are united by dense irregular connective tissue of an articular capsule, often with accessory ligaments Fibrous Joints Description of 3 types: (Sutures, Gomphosis, Syndesmosis) Sutures: (Sutra, a seam) Synarthrotic joint connected by dense fibrous connective tissue - Locates between bones of skull - EX: Coronal Suture Gomphosis:( Bolt or Nails) Synarthrotic joint binding teeth to bony sockets in maxillae and mandible Syndesmosis: (A band or Ligament) Amphiarthrotic joint with bones connected by dense irregular connective tissue such as a ligament - Ex: Distal joint b/w Tibia & Fibula Cartilaginous Joints Description of 2 types: (Symphyses, Synchondrosis) Symphyses: (Growing Together)” Articulating bones are covered by hyaline cartilage with a broad flat disc of fibrocartilage connecting the bones - All occur in Mid-line of body - All are Amphiarthrotic joints - EX: Joint between the two pubic bones Synchondrosis: (held together by cartilage) Synarthrotic joint formed by a ridged, cartilaginous Bridge between two articulating bones - Typically, Hyaline Cartilage - EX: Growth plate connecting epiphysis and diaphysis of long bone - EX: B/W ends of the first pair of ribs and the sternum Bony Joint Synostosis: Synarthrotic, totally rigid, immovable joint; formed when bone fuse EX: (1) Frontal suture between the two frontal bones after ossification closing the anterior fontanelle. (2) The fusion of the epiphyseal plates to become the epiphyseal lines Synovial Joints Are diarthrotic joints between the ends of long bone which have a distinct synovial cavity with fluid, and with articular cartilage covering the bone articulating surfaces - Functionally: Diarthroses - Permit wider range of motion than any mother joint type - Located at the ends of long bones 8.2: Synovial joints are freely movable and lines with a synovial membrane Components of a Synovial Joint: Articular Cartilage: Covers bones at joint; structure resembles hyaline cartilage but with no perichondrium Joint Capsule, or Articular capsule: is a sleeve-like capsules that (1) Surrounds a Synovial joints (2) Encloses the synovial cavity of the joint (3) Unites the articulating bones The outer Fibrous Membrane: composed of dense irregular connective (collagen) that attaches the capsule to the periosteum of the articulating bones. Fiber bundles form ligaments and tendons that give synovial joints mechanical strength & mobility Inner Synovial Membrane: lines the interior of the joint capsule; secretes synovial fluid into the joint cavity Synovial Fluid: Clear, straw- colored, viscous fluid; consistency of raw egg - Viscosity due to high concentration of hyaluronic acid - Produced by synovial membrane - Circulates from areolar tissue into joint cavity - Percolates through articular cartilage (providing oxygen and nutrients to chondrocytes; carries away metabolic wastes) Joint Cavity: Fluid lubricates, cushions, prevents abrasions, and supports chondrocytes; total volume of synovial fluid in a joint in normally less than 3 ml. Functions of synovial Fluid (1) Lubrication for Friction Reduction: Under compression, fluid squeezes out of the cartilage and into space between bones; layer of fluid reduces friction (2) Shock Absorption: Viscosity increases with increasing pressure (3) Nutrient Distribution: Circulates continuously, providing nutrients and carrying away waste; Compression and expansion of articular cartilage assist in circulation (4) Contains Phagocytic Cells: to remove microbes and debris In complex synovial joints, such as the knee, a variety of accessory structures provide support and additional stability; Tendon of the quadricep muscle is not a part of the knee itself, but limits range of motion and provides mechanical support. Accessory Structures Supporting the knee (1) Bursa: Small, thin, fluid filled pocket filled with synovial fluid, lined by synovial membrane; forms in connective tissue outside a joint capsule; reduces friction; acts a shock absorber; Bursitis is an inflammation of a bursa Tendon Sheaths: Are tube-like bursa that wrap around certain tendon to reduce friction at joints (2) Fat Pads: Localized masses of adipose tissue covered by layer of synovial membrane; usually superficial to joint capsule; protect articular cartilage; fills in spaces created as joint moves and joint cavity changes shape (3) Meniscus or Articular Disk: Pad of fibrocartilage between opposing bones ina synovial joint Functions of meniscus: Subdivide the synovial cavity; provide tighter fit of two bones; improve stability of joint; cause the directing of synovial fluid to areas of greatest friction (4) - Accessory Ligaments: Support, strengthen, and reinforce synovial joints Capsular Ligaments: or Intrinsic ligaments; localized thickenings of the joint capsule Extrinsic Ligaments: separate from the joint capsule Extracapsular Ligaments: pass outside the joint capsule; EX: Patellar ligament Intracapsular Ligaments: pass inside the joint capsule, EX: Cruciate ligaments Mobility in Joints: Greater range of motion results in weaker joint  Synarthroses are stronger joints and have no movement  Diarthroses are the most mobile joints and the weakest Dislocation, or Luxation  Movement beyond the normal range of motion  Articulating surfaces forced out of position  Damages joint structures  Pain is from nerves monitoring capsule and surrounding tissue  (No pain receptor inside a joint) 8.3: Anatomical Organization determines the motion at synovial joint Types of Synovial Joints Plane Joint: Plane joint, or gliding joints, have flattened or slightly curved surfaces that slide across one another, but the movement is very slight. - Movement: Gliding; Slight monaxial - EX: sacroiliac joints Hinge Joint: Hinge joints permit angular motion in a single plane, like the opening and closing of a door. - Movement: Angular, monaxial - EX: Elbow joint, knee joint, ankle joint, interphalangeal joints Pivot Joint: Pivot joints permit only rotation - Movement: Rotation; monaxial - Ex: Atlanto-Axial joint; Proximal Radio- ulnar joints Condylar Joint: Condylar joints have an oval articular face nestled within a depression on the opposing surface - Movement Angular; Biaxial - EX: Radiocarpal Joints Saddle Joints: Saddle joints have articular faces that fit together like a rider in a saddle. Each face is concave along one axis and convex along another - Movement: Angular, Biaxal EX: First Carpometacarpal Ball- and- Socket Joint: In a ball-and-Socket joint, the round head of one bone rest within a sup-shaped depression in another - Movement: Angular, Circumduction; and rotation: Triaxial - EX: Shoulder joints, Hip Joints 8.4: Specific terms are used to describe movements with reference to the anatomical position Flexion & Extension: Refer to movement at hinge joints of the long bones of the limbs Flexion: Decreases the angle of the joint Extension: Increases the angle of the joint Hyperextension: Extension past the anatomical region Lateral Flexion: Refers to bending the vertebral column to the side; Most pronounced in Cervical and thoracic regions Movements of the Foot Dorsiflexion: (Ankle Flexion) upward movement of foot or toes Plantar Flexion (Planta, Sole) movement extending the ankle, as in standing on tiptoe Abduction & Adduction: Refer to movements of the appendicular skeleton Abduction:(Ab, From) Movement away from the longitudinal axis in the frontal plane Adduction (Ad, To) Movement toward the longitudinal axis in the frontal plane Circumduction: Moving a body part such that the distal end traces a circle while the proximal end stays in one position 8.5: Specific terms describe rotation and Special Movements Rotation: When referring to the truck, described as left and right rotation - Described in reference to anatomical position When referring to the limbs. Described as Medial & lateral Rotation Medial Rotation: (Internal, or inward, rotation) Anterior surface of a limb turns toward the long axis of the trunk Lateral Rotation: (External, or Outward, rotation) Anterior surface of a limb turns away from the long axis of the trunk Special Terms For the rotation of the forearm Movement occurs at the proximal joint between radius and ulna; radial head rotates Pronation: Distal Epiphysis of radius rolls across the anterior surface of the ulna; Turns the wrist and hand from palm facing front to palm facing back (Posteriorly) Supination: Opposing movement; palm is turned anteriorly Special Movements Opposition: Movements of the thumb toward the surface of the palm or pads of other fingers; enables grasping object Movements of the foot: Inversion & Eversion Inversion: Twisting motion turning the sole inward Eversion: opposing motion turning the sole outward Protraction: Moving a part of the body anteriorly in the horizontal plane Retraction: Reverse of protraction; returning the body part to normal position Depression: Moving a body part inferiorly (As in opening your Jaw) Elevation: moving a body part superiorly (As in closing your Jaw) Section 2: Axial & Appendicular Joints 8.6: Axial Joints have less range of motion than appendicular joint Joints of Axial Skeleton Strong joints; permit very little movement. - Ex Atlanto- Occipital Joint (Articulation b/w occipital bone and Atlas); Articulation b/w C1 & C2 Joints of Appendicular Skeleton Extensive range of motion; Often weaker than Axial Skeleton joints - Ex: Sternoclavicular Joint (articulation between the axial skeleton and pectoral gridle and upper limb - Sacro-iliac Joint (Attaches the sacrum of axial skeleton to the pelvic gridle 8.7: The Vertebral column includes Three types of joints Three types of joints in Vertebral Column Syndesmoses (of Vertebral column): Fibrous joints, including vertebral ligaments Synchondroses (of Vertebral Column): Intervertebral joints, forming intervertebral disc - Accounting for ¼. Length of vertebral column - With increase age, water content decreases; loss of cushioning ability increases risk of vertebral injury; vertebral column also shortens Synovial (of vertebral column): Joints between bony processes Intervertebral Disc Components Anulus Fibrosus: Tough outer ring of fibrocartilage; collagen fibers attach to adjacent vertebrae Nucleus Pulposus: Soft, elastic, gelatinous core; gives disc resilience and shock absorption ability 8.8: Clinical Module: Intervertebral disc disease and osteoporosis are common age-related health problems; Vertebral abnormalities Intervertebral Disc Disease (IVDD) is a painful condition associated with disc degeneration that affects the spinal nerves. Causes include a Bulging disc or Herniated disc Bulging Disk: Caused by weakened posterior longitudinal ligaments; allows compression of nucleus pulposus and distortions of alnus fibrosus; Tough, outer layer of cartilage bulges laterally Herniated Disc: Nucleus pulpous breaks through anulus fibrosus and protrudes into the vertebral canal; compresses spinal nerves Bone Changes with aging Osteopenia (Penia, lacking): inadequate ossification leading to loss of bone mass; often occurs with age; beginning between ages 30 & 40; more severe in women than men Osteoporosis (Porous; Porous): Bone loss sufficient to affect normal function *Loss of bone mass, along with reduced cushioning of intervertebral disc, leads to increasing of vertebral fractures in elderly 8.9: The shoulder & Hip are ball-and-socket joints Shoulder joint, or glenohumeral joint: - Greatest range of motion of any joint - most frequently dislocated joint (demonstrates how stability is sacrificed for mobility) Ball-and-socket Diarthrosis: - Articulation between the head of the humerous and the glenoid cavity of the scapula - Stabilized by five major ligaments, surrounding muscles, and associated tendons - Bursae help reduce friction: Tendon of the bicep brachii surrounded by a tubular bursa as it passes through the articular capsule Glenohumeral joint stabilizing ligaments - Coracoclavicular ligaments Acromioclavicular ligament Coraco-acromial ligament Coracohumeral ligament Glenohumeral ligaments Glenohumeral joint features Articular capsule: Permits extensive range of motion; small articular cartilage Glenoid Labrum (labrum, lip or edge): Fibrocartilage rim; increases area of the glenoid cavity Hip joint Sturdy ball-and-socket diarthrosis joint; permits flexion, extension, adduction, abduction. Articulation between the head of the femur and the acetabulum (Deep Fossa) of the hip bone Acetabular Labrum: Rim of fibrocartilage; increases the depth of the joint cavity; helps to seal in synovial fluid Articular Capsule of the hip: Extends from the lateral and inferior surfaces of the pelvic griddle to the intertrochanteric line and intertrochanteric crest of femur; reinforced by five ligaments Hip Joint Reinforcing Ligaments (1) Transverse acetabular ligament: Crosses the acetabular notch, filling gap in the inferior border of the acetabulum (2) Ligamentum Teres: “Ligament of femoral head” ; originates along the transverse acetabular ligament; attaches to the fovea capitis (3) Pubofemoral ligaments (4) Iliofemoral ligaments (5) Ischiofemoral ligament 8.10: The Elbow & Knee are hinge joints Elbow Joint Complex hinge joint involving humerous, radius, and ulna; Extremely stable because: (1) The bony surfaces of the humerous and Ulna interlock (2) A single, thick articulation capsule surrounds both the humero-ulnar and proximal radioulnar joint s (3) Strong ligaments reinforce the articular capsule Specific Joints of the Elbow: Humeroradial joint: Capitulum of humerous articulates with head of radius Humero-Ulnar joint: Largest and strongest articulation ; works like a door hinge, where trochlea of humerus articulates with trochlear notch of the ulna - Shape of the trochlear notch determines the plane of movement - Shapes of olecranon fossa and olecranon limit the degree of extension Proximal radio-Ulnar joint is not part of the elbow joint; Capsule and ligaments help hold the Humerous, Ulna, and Radius in position Muscle attachments - Muscles that extend that elbow attach on the olecranon on the posterior surface - Controlled by the radial nerve - Tendon of the biceps brachii attaches at the radial tuberosity - Contraction produces supination of forearm and flexion at the elbow Severe stresses can still produce dislocation or other injuries, especially when epiphyseal growth is not complete - Examples Nursemaid’s Elbow: Partial dislocation of the Radial Head from Annular ligament Elbow Joint Reinforcing Ligaments Radial Collateral ligament: Stabilized the lateral surface of the elbow Annular Ligaments: binds the head of the radius to the Ulna Ulnar Collateral Ligament: Stabilizes the medial surface of the elbow joint Knee Joint: Contains three separate articulations 1. Medial Condyle of Tibia to medial condyle of femur 2. Lateral condyle of tibial to lateral condyle of femur 3. One between the Patella and Patellar surface of the femur These articulations permit flexion, extension, and very limited rotation (Fibula is not part of the knee) Knee Joints Supporting Structures Quadriceps Tendon: Continues as patellar ligament to anterior tibial surface Fibular Collateral ligament, or Lateral collateral ligament (LCL): Provides lateral support Tibial Collateral Ligament, or Medial Collateral ligament (MCL): Provides medial support Popliteal ligaments: Run between femur and heads of the tibia and fibula Medial and Lateral menisci: Pair of fibrocartilage pads; Located between femoral and tibial surfaces; Acts as cushions and provides lateral stability Anterior Cruciate Ligament (ACL): At full extension, slight lateral rotation of Tibia tightens ACL and forces lateral meniscus between tibia and femur - This “locks” knee in extended position - Opposite motion required to “Unlock” Posterior Cruciate ligament (PCL) 8.11: Clinical Module: Arthritis can disrupt normal joint structure and function Terminology Rheumatism: General term indicating pain and stiffness in the bones and/or muscles Arthritis: All rheumatic diseases that affect synovial joints, always involves damage to the articular cartilage; causes vary. - Three types: (Osteoarthritis, rheumatoid Arthritis, Gouty Arthritis) Osteoarthritis: Also known as degenerative arthritis or degenerative joint disease (DJD); most common form of arthritis, generally affects individuals aged 60 or older - In the U.S, affects 25 percent of women and 15 percent of men over age of 60 - Caused by: Cumulative effects of wear & tear on joints; genetic factors affecting collagen formation Joint changes with Arthritis Normal Articular cartilage: Smooth, slick surface; Thick cartilage with homogeneous matrix Articular Cartilage damaged by Osteoarthritis: Rough, bristly collagen fibers on the surface; increases friction at the joint; promotes further degradation Visualization of problematic joints Arthroscope: Narrow, flexible fiberoptic tube with tiny camera. Allows exploration of a joint without major surgery. May be used in combination with other flexible instruments inserted through additional incisions to conduct surgery - Called Arthroscopic Surgery Magnetic Resonance Imaging (MRI) : Allows visualization of soft tissue outside the joint cavity, not visible with arthroscope, cost- effective; noninvasive Artificial Joints: May be method of last resort for arthritis treatment if other methods fail to slow disease progression. Other methods include regular exercise, physical therapy, antiinflammatory drugs. Can restore mobility and relieve pain. High impact activates are restricted after replacement. New joints (Hips/knees) can last more than 15 years