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Understanding Joint Classification and Functions

Learn about the types of joints, their classification, and structures. Discover how synovial, fibrous, and cartilaginous joints differ in movement and function. Explore representative synovial joints like the shoulder and elbow joints.

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Understanding Joint Classification and Functions

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  1. Chapter 9: Articulations

  2. INTRODUCTION Articulation: point of contact between bones Joints are mostly movable, but some are immovable or allow only limited motion Movable joints allow complex, highly coordinated, purposeful movements to be executed

  3. CLASSIFICATION OF JOINTS Joints may be classified by using a structural or functional scheme (Table 9-1) Structural classification: joints are named according to: Presence of a fluid-filled joint capsule (synovial joint) Type of connective tissue that joins bones together (fibrous or cartilaginous joints) Functional classification: joints are named according to the degree of movement allowed Synarthroses: immovable joint Amphiarthroses: slightly movable Diarthroses: freely movable

  4. CLASSIFICATION OF JOINTS (cont.) Fibrous joints (synarthroses): bones of joints fit together closely, thereby allowing little or no movement (Figure 9-1) Syndesmoses: joints in which ligaments connect two bones Sutures: found only in the skull; teethlike projections from adjacent bones interlock with each other Gomphoses: between the root of a tooth and the alveolar process of the mandible or maxilla

  5. CLASSIFICATION OF JOINTS (cont.) Cartilaginous joints (amphiarthroses): bones of joints are joined together by hyaline cartilage or fibrocartilage; allow very little motion (Figure 9-2) Synchondroses: hyaline cartilage present between articulating bones Symphyses: joints in which a pad or disk of fibrocartilage connects two bones

  6. CLASSIFICATION OF JOINTS (cont.) Synovial joints (diarthroses): freely movable joints (Figure 9-3) Structures of synovial joints Joint capsule: sleevelike casing around the ends of the bones Synovial membrane: membrane that lines the joint capsule and secrete fluid Articular cartilage: cartilage covering the articular surfaces of bones

  7. CLASSIFICATION OF JOINTS (cont.) Synovial joints (diarthroses): freely movable joints (Figure 9-3) Structures of synovial joints contd Joint cavity: small space between the articulating surfaces of the two bones of the joint Menisci (articular disks): pads of fibrocartilage located between articulating bones Ligaments: strong cords of dense, white, fibrous tissue that hold the bones of a synovial joint more firmly together Bursae: synovial membranes filled with synovial fluid; cushion joints and facilitate movement of tendons Cartilage: firm, whitish, flexible connective tissue found in various forms in the articulating surfaces of join

  8. CLASSIFICATION OF JOINTS (cont.) Synovial joints (cont.) Types of synovial joints (Figure 9-4) Uniaxial joints: synovial joints that permit movement around only one axis and in only one plane Hinge joints: articulating ends of bones form a hinge-shaped unity that allows only flexion and extension Pivot joints: a projection of one bone articulates with a ring or notch of another bone Biaxial joints: synovial joints that permit movements around two perpendicular axes in two perpendicular planes Saddle joints: synovial joints in which the articulating ends of the bones resemble reciprocally shaped miniature saddles; only example in the body is in the thumb Condyloid (ellipsoidal) joints: synovial joints in which a condyle fits into an elliptical socket

  9. CLASSIFICATION OF JOINTS (cont.) Types of synovial joints (cont.) Multiaxial joints: synovial joints that permit movements around three or more axes in three or more planes Ball-and-socket (spheroid) joints: most movable joints; the ball-shaped head of one bone fits into a concave depression Gliding joints: relatively flat articulating surfaces that allow limited gliding movements along various axes

  10. REPRESENTATIVE SYNOVIAL JOINTS Humeroscapular joint (Figure 9-5) Shoulder joint Most mobile joint because of the shallowness of the glenoid cavity Glenoid labrum: narrow rim of fibrocartilage around the glenoid cavity that lends depth to the glenoid cavity Structures that strengthen the shoulder joint are ligaments, muscles, tendons, and bursae

  11. REPRESENTATIVE SYNOVIAL JOINTS (cont.) Elbow joint (Figure 9-6) Humeroradial joint: lateral articulation of the capitulum of the humerus with the head of the radius Humeroulnar joint: medial articulation of the trochlea of the humerus with the trochlear notch of the ulna Both components of the elbow joint surrounded by a single joint capsule and stabilized by collateral ligaments Classic hinge joint Medial and lateral epicondyles are externally palpable bony landmarks Olecranon bursa independent of elbow joint space; inflammation called olecranon bursitis Trauma to nerve results in unpleasant sensations in the fingers and part of the hand supplied by the nerve; severe injury may cause paralysis of hand muscles or reduction in wrist movements

  12. REPRESENTATIVE SYNOVIAL JOINTS (cont.) Proximal radioulnar joint: between the head of the radius and the medial notch of the ulna Stabilized by the annular ligament Permits rotation of the forearm Dislocation of the radial head called a pulled elbow Distal radioulnar joint: point of articulation between the ulnar notch of the radius and the head of the ulna Acting with the proximal radioulnar joint permits pronation and supination of the forearm

  13. REPRESENTATIVE SYNOVIAL JOINTS (cont.) Radiocarpal (wrist) joints (Figure 9-7) Only the radius articulates directly with the carpal bones distally (scaphoid and lunate) Joints are synovial Scaphoid bone is fractured frequently Portion of the fractured scaphoid may become avascular

  14. REPRESENTATIVE SYNOVIAL JOINTS (cont.) • Intercarpal joints • Present between eight carpal bones • Stabilized by numerous ligaments • Joint spaces usually communicate • Movements generally gliding with some abduction and flexion

  15. REPRESENTATIVE SYNOVIAL JOINTS (cont.) Carpometacarpal joints: total of three joints One joint for the thumb—wide range of movements Two joints for the fingers—movements largely gliding type Thumb carpometacarpal joint is unique and important functionally Loose-fitting joint capsule Saddle-shaped articular surface Movements: extension, adduction, abduction, circumduction, and opposition Opposition: ability to touch the tip of the thumb to the tip of other fingers; movement of great functional significance

  16. REPRESENTATIVE SYNOVIAL JOINTS (cont.) • Metacarpophalangeal joints (Figure 9-8) • Rounded heads of metacarpals articulate with concave bases of the proximal phalanges • Capsule surrounding joints strengthened by collateral ligaments • Primary movements are flexion and extension

  17. REPRESENTATIVE SYNOVIAL JOINTS (cont.) Interphalangeal joints Typical diarthrotic, hinge-type, synovial joints Exist between heads of phalanges and bases of more distal phalanges Two categories: Proximal interphalangeal joints: between proximal and middle phalanges Distal interphalangeal joints: between middle and distal phalanges

  18. Hip joint (Figure 9-9) Stable joint because of the shape of the head of the femur and the acetabulum A joint capsule and ligaments contribute to the joint’s stability Knee joint (Figures 9-10 and 9-11) Largest and one of the most complex and most frequently injured joints Tibiofemoral joint is supported by a joint capsule, cartilage, and numerous ligaments and muscle tendons Permits flexion, extension and, with the knee flexed, some internal and external rotation REPRESENTATIVE SYNOVIAL JOINTS (cont.)

  19. REPRESENTATIVE SYNOVIAL JOINTS (cont.)- last one Ankle joint (Figure 9-12) Synovial-type hinge joint Articulation between the lower ends of the tibia and fibula and the upper part of the talus Joint is mortise, or wedge, shaped Lateral malleolus lower than medial malleolus Internal rotation injury results in common “sprained ankle” Involves anterior talofibular ligament Other ankle ligaments also may be involved in sprain injuries (e.g., deltoid ligament) External ankle rotation injuries generally involve bone fractures rather than ligament tears First-degree ankle injury: lateral malleolus fractured Second-degree ankle injury: both malleoli fractured Third-degree ankle injury: fracture of both malleoli and articular surface of tibia

  20. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS Measuring range of motion (Figure 9-15) Range of motion (ROM) assessment used to determine extent of joint injury ROM can be measured actively or passively; both are generally equal ROM measured by instrument called a goniometer Angular movements change the size of the angle between articulating bones Flexion: decreases the angle between bones; bends or folds one part on another (Figures 9-16,9-18, and 9-19) Extension and hyperextension Extension: increases the angle between bones; returns a part from its flexed position to its anatomical position Hyperextension: stretching or extending part beyond its anatomical position (Figures 9-19, 9-21, and 9-23)

  21. Flexion: decreases the angle between bones; bends or folds one part on another (Figures 9-16,9-18, and 9-19) • Extension and hyperextension • Extension: increases the angle between bones; returns a part from its flexed position to its anatomical position • Hyperextension: stretching or extending part beyond its anatomical position (Figures 9-19, 9-21, and 9-23)

  22. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS (cont.) Plantar flexion and dorsiflexion (Figure 9-25) Plantar flexion increases the angle between the top of the foot and the front of the leg Dorsiflexion decreases the angle between the top of the foot and the front of the leg Abduction and adduction (Figures 9-19 and 9-23) Abduction moves a part away from the median plane of the body Adduction moves a part toward the median plane of the body

  23. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS (cont.) Circular movements Rotation and circumduction Rotation: pivoting a bone on its own axis (Figure 9-16, D) Circumduction: moves a part so that its distal end moves in a circle Supination and pronation (Figure 9-20, B) Supination turns the hand palm side up Pronation turns the hand palm side down Gliding movements: simplest of all movements; articular surface of one bone moves over the articular surface of another without any angular or circular movement

  24. TYPES AND RANGE OF MOVEMENT AT SYNOVIAL JOINTS (cont.) Special movements Inversion and eversion (Figure 9-25, B) Inversion: turning the sole of the foot inward Eversion: turning the sole of the foot outward Protraction and retraction (Figure 9-17, A) Protraction moves a part forward Retraction moves a part backward Elevation and depression (Figure 9-17, B) Elevation moves a part up Depression lowers a part

  25. CYCLE OF LIFE: ARTICULATIONS Bone development and the sequence of ossification between birth and skeletal maturity affect joints Fontanels between cranial bones disappear Epiphysial plates ossify at maturity Older adults ROM decreases Changes in gait Skeletal diseases manifest as joint problems Abnormal bone growth (lipping) influences joint motion Disease conditions can be associated with specific developmental periods

  26. Key points for chapter 9 Hand: “reason for the upper extremity”; thumb: “reason for the hand” Examples of “big picture” type of thinking when used in functional context Mobility of the upper extremity is extensive because of the following: Arrangement of bones in the shoulder girdle, arms, forearm, wrist, and hand Location and method of attachment of muscles to bones Proper functioning of joints Mobility and extensive ROM needed to position upper extremity and hand to permit grasping and manipulation of objects, thus enabling effective interaction with objects in the external environment

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