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Anatomy of a Joint

Illustration of the anatomy of the hip joint
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Joints are the areas where two or more bones meet. Most joints are mobile, allowing the bones to move. Joints consist of the following:

  • Cartilage  -  a type of tissue that covers the surface of a bone at a joint. Cartilage helps reduce the friction of movement within a joint.

  • Synovial membrane  -  a tissue called the synovial membrane lines the joint and seals it into a joint capsule. The synovial membrane secretes synovial fluid (a clear, sticky fluid) around the joint to lubricate it.

  • Ligaments  -  strong ligaments (tough, elastic bands of connective tissue) surround the joint to give support and limit the joint's movement.

  • Tendons  -  tendons (another type of tough connective tissue) on each side of a joint attach to muscles that control movement of the joint.

  • Bursas  -  fluid-filled sacs, called bursas, between bones, ligaments, or other adjacent structures help cushion the friction in a joint.

  • Synovial fluid  -  a clear, sticky fluid secreted by the synovial membrane.

  • Femur  -  the thighbone.

  • Tibia  -  the shin bone.

  • Patella  -  the kneecap.

  • Meniscus  -  a curved part of cartilage in the knees and other joints.

Illustration of types of joints
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What are the different types of joints?

There are many types of joints, including joints that do not move in adults, such as the suture joints in the skull. Joints that do not move are called "fixed." Other joints may move a little, such as the vertebrae. Examples of mobile joints include the following:

  • Ball-and-socket joints
    Ball-and-socket joints, such as the shoulder and hip joints, allow backward, forward, sideways, and rotating movements.

  • Hinge joints
    Hinge joints, such as in the fingers, knees, elbows, and toes, allow only bending and straightening movements.

  • Pivot joints
    Pivot joints, such as the neck joints, allow limited rotating movements.

  • Ellipsoidal joints
    Ellipsoidal joints, such as the wrist joint, allow all types of movement except pivotal movements

Online Resources

National Institute of Arthritis and Musculoskeletal and Skin Diseases  http://www.niams.nih.gov/health_info/osteoarthritis/default.asp#4

© 2000-2011 Krames StayWell, 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.