Articulations ~ Joints

http://www.argosymedical.com/flash/synovial_joints/landing.html

Definition

Bones can move because of the way they are joined together. The place where two or more bones come together is called a joint. The bones at a joint are held together by strong bands of tissue called ligaments which allow the bones to move. However, there are several different kinds of joint, and each one moves differently.

Types of JointsFibrous joints connect bones without allowing any

movement. The bones of your skull and pelvis are held together by fibrous joints. The union of the spinous processes and vertebrae are fibrous joints.

Cartilaginous joints are joints in which the bones are attached by cartilage. These joints allow for only a little movement, such as in the spine or ribs.

Synovial joints allow for much more movement than cartilaginous joints. Cavities between bones in synovial joints are filled with synovial fluid. This fluid helps lubricate and protect the bones. Bursa sacks contain* the synovial fluid.

Ball and Socket

The ball-and-socket joint is found in the hip-bone and the shoulder and allows the most movement of all the joints. One bone has a ball-like knob at the end of it, and the knob fits into a cup-like space on the other side. The ball-and-socket joint is what allows baseball pitchers to throw a ball with such tremendous speed.

Gliding movements

Intercarpal joints

Sliding ~Gliding

The sliding joint is found in the vertebral column and allows small sliding movements. The vertebrae have pads of cartilage between them, and the bones slide over these pads. This is what makes the backbone so flexible.

Pivot

The pivot joint allows movement turning from side to side, and your head is attached to your vertebral column with this joint. A hole in one bone fits over a pointed part of the other bone, so that one bone can turn on top of the other.

Pivot

Rotation of one bone around another

Atlas and Axis

Hinge

The hinge joint allows bones to move back and forth, and is found in your elbow and knee. It allows bones to move like a hinge in a door.

Condyloid - Similar to the ball and socket joint, the condyloid joint allows circular motion. In the condyloid joint, the ball rests up against the end of a bone rather than inside a socket. Example: The carpals of the WRIST rest against the end of the RADIUS bone of the forearm.

Saddle - The saddle joint allows movement in various directions. For example, where the THUMB meets the wrist the bones fit up against each other like a saddle fits over the back of a horse.

It might seem funny, but there is one type of joint which doesn't allow any movement at all. A joint between bones that do not move at all is called a fixed joint, and one place the fixed joint is found is in your skull. When babies are born, their skull bones are not joined together yet. In fact, there is a gap between them called the fontanel, or soft spot. However, the bones quickly grow together to protect the brain.

Review 1

1. fixed joint

2. pivot joint

3. ball-and-socket joint

4. sliding joint

5. hinge joint

A painful sacroiliac joint is one of the more common causes of mechanical low back pain. Sacroiliac (SI) joint dysfunction is a term that is used to describe the condition - because it is still unclear why this joint becomes painful and leads to low back pain. Sacroiliac joint dysfunction can be a nuisance but it is seldom dangerous and rarely leads to the need for surgery.

Review 2

Ball and Socket

Condyloid

Hinge

Pivot

Saddle