Anatomy of the Joints

The joints of the body include the various connective tissues that facilitate the movement of the moving skeletal bones of the body, as well as support for the skeletal bones as they move and press against one another. These joints provide separation of the bones, so that they don't contact and grind against one another. When friction does occur between the bones, this is the most common cause of osteoarthritis. Various things can be done to prevent osteoarthritis, though some wear and tear of the cartilage in the joints in inevitable, due to the natural aging process. Let's take a look at the anatomy of the joints, including the vital tissues such as the cartilage, synovial membrane, tendons, ligaments, bursas, and synovial fluid.

Cartilage: The cartilage provides the cushioning and support between the weight-bearing bones of the body. These tissues absorb the pressure of bones that are pressed towards one another, such as the femur and tibia of the leg as we walk and run. This joint tissue covers the surface of a bone at a joint. Cartilage provides a surface to prevent friction between moving bones that are bending around one another or gliding across one another.

Synovial membrane: The synovial membrane lines the joint and seals the entire joint within a joint capsule. This membrane secretes a sticky, clear fluid that is spread around the joint and lubricates it.

Synovial fluid: synovial fluid is secreted by the synovial membrane and is designed to perform three functions so that the cartilage in the joint capsule does not erode or become incurred.

  1. Reduction of friction - this slippery fluid coats the surfaces of the joint cartilage to minimize or eliminate friction.
  2. Shock absorption - This fluid responds differently to different types of pressure that are applied to the joints, so that the substances actually changes to take on more weight-bearing responsibilities, depending on the requirements of the body. When greater amounts of pressure are placed upon certain joints, the synovial fluid becomes thick to increase the joint's shock absorption properties.
  3. Waste transportation and nutrient transportation - All of the tissues within the joint capsule are living tissues, which need nutrients and energy to function. These tissues also need a system to transport the waste products of cellular respiration away from the joints, as well as old cells which have become worn out or injured. Unlike the bone and muscles, the joint tissues do not have direct access to the blood vessels. The synovial membrane provides this function in the joints.
Ligaments and Tendons: Ligaments and tendons are tough, elastic bands of connective tissue that connect to the bones, facilitate movement, and provide support against excessive movement. Ligaments connect muscles to bone. Tendons connect bone to bone. Ligaments surround the joint and limit the joint's movement. Tendons attach to each side of the joint and control the joint's movements.

Bursas: the bursas are another type of structure that is designed to reduce friction between the bones, tendons, and ligaments. The bursas are fluid-filled sacs that are placed between, ligaments, bones and other adjacent structures and save the joint from wear and tear.

Meniscus: the meniscus is a curved part of cartilage in the knees and other joints. In the human knee, pair of menisci is slightly bowl shaped and separate the medial and lateral condyles in each femur and tibia. The menisci are composed of cartilaginous tissue and provide an additional layer of protection to this weight-bearing lower body joint.

Different types of joints: the different types of joints in the body are classified according to the different types of movements that allow. For example, the joints in the shoulder and hip joints are known as ball and socket joints. These joints allow for movement in every direction. Hinge joints are those in the knees, elbows, and fingers and allow for flexion and extension only. Pivot joints, such as those found in the neck, allow limited rotating movements. Ellipsoidal joints allow every type of movement except for pivotal movements.