Synovial or Freely Movable Joints

• Those joints in which the articulating bones are separated by a fluid containing joint cavity
• All are freely movable diarthroses
• Examples – all limb joints, and most joints of the body

Synovial Joints: General Structure

Synovial joints all have the following:

• Articular cartilage
• Joint (synovial) cavity
• Articular capsule
• Synovial fluid
• Reinforcing ligaments

1. 1.2.1.3.1 Types of Synovial Joints
2. The six types of synovial joints
3. Pivot joints allow for rotation around an axis, such as between the first and second cervical vertebrae, which allows for side-to-side rotation of the head.
4. The hinge joint of the elbow works like a door hinge.
5. The articulation between the trapezium carpal bone and the first metacarpal bone at the base of the thumb is a saddle joint.
6. Planar (or plane) joints, such as those between the tarsal bones of the foot, allow for limited gliding movements between bones
7. The radiocarpal joint of the wrist is a condyloid joint or Ellipsoidal joint.
8. The hip and shoulder joints are the only ball-and-socket joints of the body.
9. Pivot Joints

• Pivot joints consist of the rounded end of one bone fitting into a ring formed by the other bone.
• This structure allows rotational movement, as the rounded bone moves around its own axis.
• An example of a pivot joint is the joint of the first and second vertebrae of the neck that allows the head to move back and forth. The joint of the wrist that allows the palm of the hand to be turned up and down is also a pivot joint.

1. Hinge Joints

• In hinge joints, the slightly-rounded end of one bone fits into the slightly-hollow end of the other bone.
• In this way, one bone moves while the other remains stationary, similar to the hinge of a door.
• The elbow is an example of a hinge joint. The knee is sometimes classified as a modified hinge joint.

1. Saddle Joints

• Each bone in a saddle joint resembles a saddle, with concave and convex portions that fit together.
• Saddle joints allow angular movements similar to condyloid joints, but with a greater range of motion.
• An example of a saddle joint is the thumb joint, which can move back and forth and up and down; it can move more freely than the wrist or fingers.

1. Planar Joints

• Planar joints have bones with articulating surfaces that are flat or slightly curved.
• These joints allow for gliding movements; therefore, the joints are sometimes referred to as gliding joints.
• The range of motion is limited and does not involve rotation.
• Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot, as well as between vertebrae.

1. Condyloid Joints or Ellipsoidal joint

• Condyloid joints consist of an oval-shaped end of one bone fitting into a similarly oval-shaped hollow of another bone.
• This is also sometimes called an ellipsoidal joint.
• This type of joint allows angular movement along two axes, as seen in the joints of the wrist and fingers, which can move both side to side and up and down.

1. Ball-and-Socket Joints

• Ball-and-socket joints possess a rounded, ball-like end of one bone fitting into a cup-like socket of another bone.
• This organization allows the greatest range of motion, as all movement types are possible in all directions.
• Examples of ball-and-socket joints are the shoulder and hip joints.

Figure 5- Types of Synovial Joints