Types of Synovial Joints

There are six types of synovial joints with distinctive patterns of motion determined by the shapes of the articular

Figure 9.6 Structure of a Simple Synovial Joint.

Why is a meniscus unnecessary in an interphalangeal joint?

11 burs = purse

Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

300 Part Two Support and Movement

300 Part Two Support and Movement

Synovial Joint Hand
Figure 9.7 Tendon Sheaths and Other Bursae in the Hand and Wrist.

surfaces of the bones (fig. 9.8; table 9.1). A bone's movement at a joint can be described with reference to three mutually perpendicular planes in space (x, y, and z). If the bone can move in only one plane, the joint is said to be monaxial; if it can move in two planes, the joint is biaxial; and if three, it is multiaxial.

  1. Ball-and-socket joints. These occur at the shoulder and hip, where one bone has a smooth hemispherical head that fits within a cuplike depression on the other. The head of the humerus fits into the glenoid cavity of the scapula, and the head of the femur fits into the acetabulum of the os coxae. These are the only multiaxial joints of the skeleton.
  2. Hinge joints. At a hinge joint, one bone has a convex surface that fits into a concave depression of the other one. Hinge joints are monaxial—like a door hinge, they can move in only one plane. Examples include the elbow, knee, and interphalangeal (finger and toe) joints.
  3. Saddle joint. The only saddle joint is the trapeziometacarpal (tra-PEE-zee-oh-MET-uh-CAR-
  4. joint at the base of the thumb. Each articular surface—on metacarpal I and the trapezium of the wrist—is shaped like a saddle, concave in one direction and convex in the other. This is a biaxial joint. If you compare the range of motion of your thumb with that of your fingers, you can see that a saddle joint is more movable than a condyloid or hinge joint. This is the joint responsible for that hallmark of primate anatomy, the opposable thumb.
  5. Pivot joints. These are monaxial joints in which one bone has a projection that fits into a ringlike ligament of another, and the first bone rotates on its longitudinal axis relative to the other. One example is the atlantoaxial joint between the first two vertebrae—the dens of the axis projects into the vertebral foramen of the atlas, where it is held against the arch of the atlas by a ligament (see fig. 8.24c). This joint pivots when you rotate your head as in gesturing "no." Another example is the proximal radioulnar joint, where the annular ligament on the ulna encircles the head of the radius (see fig. 9.20c, d) and permits the radius to

Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Chapter 9 Joints 301

Chapter 9 Joints 301

Six Synovial Joints

Figure 9.8 The Six Types of Synovial Joints. All six have representatives in the forelimb. Mechanical models show the types of motion possible at each joint.

Figure 9.8 The Six Types of Synovial Joints. All six have representatives in the forelimb. Mechanical models show the types of motion possible at each joint.

rotate during pronation and supination of the forearm (motions to be described shortly).

  1. Gliding (plane) joints. Here, the articular surfaces are flat or only slightly concave and convex. The adjacent bones slide over each other and have rather limited monaxial movement; they are amphiarthroses in contrast to the other five types listed, which are diarthroses. Gliding joints occur between the carpal and tarsal bones, between the articular processes of the vertebrae, and at the sternoclavicular joint. To feel a gliding joint in motion, palpate your sternoclavicular joint as you raise your arm above your head.
  2. Condyloid (ellipsoid) joints. These joints exhibit an oval convex surface on one bone that fits into a similarly shaped depression on the next. The radiocarpal joint of the wrist and the metacarpophalangeal (MET-uh-CAR-po-fuh-LAN-jee-ul) joints at the bases of the fingers are examples. These are considered biaxial joints because they can move in two directions, for example up and down and side to side. To demonstrate, hold your hand with your palm facing you. Flex your index finger back and forth as if gesturing to someone, "come here," and then move the finger from side to side toward the thumb and away. This shows the biaxial motion of the condyloid joint.

In table 9.1 the joints are classified by structural criteria. Some joints are difficult to classify, however, because they have elements of more than one type. The jaw joint, for example, has some aspects of condyloid, hinge, and gliding joints for reasons that will be apparent later.

Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

302 Part Two Support and Movement

Table 9.1 Anatomical Classification of the Joints

Joint

Fibrous Joints

Sutures (fig. 9.4) Serrate suture

Lap suture

Plane suture Gomphosis (fig. 9.36) Syndesmosis (fig. 9.3c)

Characteristics and Examples

Adjacent bones bound by collagen fibers extending from the matrix of one into the matrix of the other

Immovable fibrous joints between cranial and facial bones

Bones joined by a wavy line formed by interlocking teeth along the margins. Examples: coronal, sagittal, and lambdoid sutures

Bones beveled to overlap each other; superficial appearance is a smooth line. Example: squamous suture around temporal bone

Bones butted against each other without overlapping or interlocking. Example: palatine suture

Insertion of a tooth into a socket, held in place by collagen fibers of periodontal ligament

Slightly movable joint held together by ligaments or interosseous membranes. Examples: tibiofibular joint and radioulnar joint

Cartilaginous Joints

Synchondrosis (fig. 9.5a)

Symphysis (fig. 9.56, c) Synostoses

Adjacent bones bound by cartilage

Bones held together by hyaline cartilage. Examples: articulation of ribs with sternum, and epiphyseal plate uniting the epiphysis and diaphysis of a long bone of a child

Slightly movable joint held together by fibrocartilage. Examples: intervertebral joints and pubic symphysis

Former fibrous or cartilaginous joints in which adjacent bones have become fused by ossification. Examples: midsagittal line of frontal bone, fusion of epiphysis and diaphysis of an adult long bone, and fusion of ilium, ischium, and pubis to form os coxae

Synovial Joints (figs. 9.6 and 9.8)

Ball-and-socket

Hinge Saddle

Pivot

Gliding

Condyloid

Adjacent bones covered with hyaline articular cartilage, separated by lubricating synovial fluid and enclosed in a fibrous joint capsule

Multiaxial diarthrosis in which a smooth hemispherical head of one bone fits into a cuplike depression of another.

Examples: shoulder and hip joints Monaxial diarthrosis, able to flex and extend in only one plane. Examples: elbow, knee, and interphalangeal joints Joint in which each bone surface is saddle-shaped (concave on one axis and convex on the perpendicular axis). Unique to the thumb (trapeziometacarpal joint), where it allows opposition (touching of the thumb to the fingertips) Joint in which a projection of one bone fits into a ringlike ligament of another, allowing one bone to rotate on its longitudinal axis. Examples: atlantoaxial joint and proximal radioulnar joint Synovial amphiarthrosis with slightly concave or convex bone surfaces that slide across each other. Examples:

intercarpal, intertarsal, and sternoclavicular joints; joints between the articular processes of the vertebrae Biaxial diarthrosis in which an oval convex surface of one bone articulates with an elliptical depression of another. Examples: radiocarpal and metacarpophalangeal joints

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Responses

  • Vilma
    What is a plane gliding joint?
    6 years ago
  • guendalina
    Is the proximal radioulnar joint multiaxial?
    6 years ago
  • sabine
    Why is a meniscus unnesccesary in aninterphalangeal joint?
    6 years ago
  • stephen
    How are the 6 types of synovial joints classified?
    6 years ago
  • bodo took-took
    Which of the joints shown in the figure is classified as a monaxial joint?
    1 year ago

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