| Osteoarthritis Basics: The Joint and Its Parts
Most joints—the place where two
moving bones come together—are designed to protect bone ends from wearing
away and to absorb shock from movements like walking or repetitive movements.
The joint
includes
- Cartilage. A hard but slippery
coating on the end of each bone. Cartilage, which breaks down and wears away in
osteoarthritis, is described in more detail in the box
Cartilage: the
Key to Healthy Joints.
- Joint capsule. A tough membrane sac
that holds all the bones and other joint parts together.
- Synovium (sin-O-vee-um). A thin
membrane inside the joint capsule.
- Synovial fluid. A fluid that
lubricates the joint and keeps the cartilage smooth and healthy.
- Muscles, ligaments, and tendons.
Together, muscles and connective tissues keep the bones stable and allow the
joint to bend and move. Ligaments are tough, cord-like tissues that connect one
bone to another. Tendons are tough, fibrous cords that connect muscles to
bones.
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| A Healthy Joint
In a healthy joint, the ends of
bones are encased in smooth cartilage. Together, they are protected by a joint
capsule lined with a synovial membrane that produces synovial fluid. The
capsule and fluid protect the cartilage, muscles, and connective
tissues.
A Joint With Osteoarthritis
With osteoarthritis, the
cartilage becomes worn away. Spurs grow out from the edge of the bone, and
synovial fluid increases. Altogether, the joint feels stiff and
sore. |
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