The Types of Moving Joints

Humans possess more than 200 joints that connect their bones. Synarthroses joints, such as the plates of the skull, don't move at all. Amphiarthroses joints, such as the vertebrae, allow moderate movement. Most of the joints of the body, however, are able to move with the help of synovial fluid, a lubricant between two joints such as the neck, shoulder, hip, knee, elbow, ankle, fingers and toes. These synovial joints, called diarthroses joints, are freely movable and are divided into six types.

Ball-and-Socket Joints

• The most common types of joints in the human body are diarthroses joints, enabling flexibility.

  The image of a ball and socket perfectly evokes the anatomy of this joint. Shoulders and hips are types of ball-and-socket joints, in which one end of the bone is rounded and fits against the concave shape of the adjoining bone for a wide range of motion. The hip joint is most likely to be effected by osteoarthritis, the most common form of arthritis, causing pain, swelling and loss of joint motion.

Condyloid or Compound Joints

• The smallest movable joints are present in fingers and toes.

  Tiny bean-shaped bones called condyles connect the bones of the palm, known as metacarpals, to the fingers, known as phalanges. The same mechanics join the foot bones, or metatarsals, to the toes, also called phalanges. Condyloid joints enable angular motion rather than rotation. Another term for condyloid joints is compound joints. Condyles are present between the skull and vertebral column and make it possible to nod your head.

Pivot Joints

• A pivot joint occurs when the rounded surface of one bone fits into the ring or tendon of another bone. The two arm bones below the elbow, called the radius and ulna, share a pivot joint. The end of the radius rotates around the axis of the ulna as the palm is turned inward and outward, as in the "royal wave." Similarly, the joint between the axis and atlas of the neck is a pivot joint so that the head can turn from side to side.

Gliding Joints

• Wrists and ankles are examples of gliding joints. Flat surfaces of these bones slide over one another, providing a limited amount of movement.

Hinge Joints

• The knee joint is especially susceptible to wear-and-tear damage and diseases such as arthritis.

  Elbows and knees are hinge joints, in which the rounded surface of one bone hugs the dished surface of another bone. Ligaments secure the sides of hinge joints, allowing the bones to move in one plane only for flexion (pull in) and extension (extend out). The knee is one of the most commonly replaced joint in the U.S.

Saddle Joint

• The thumb is the only saddle joint in the body and is more flexible than either a hinge joint or a gliding joint. Touching surfaces of these bones have both concave and convex shapes, making movement in two directions possible. For example, the thumb is able to "cross over" the palm.