National Institute of Arthritis and Musculoskeletal and Skin Diseases
Osteoarthritis Basics: The Joint and Its Parts continued...
A Joint With Severe 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.
Ligaments, tendons, and muscles are tissues that surround the bones and joints, and allow the joints 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. Muscles are bundles of specialized cells that, when stimulated by nerves, either relax or contract to produce movement.
Cartilage: The Key to Healthy Joints
Cartilage is 65 to 80 percent water. The remaining three components – collagen, proteoglycans, and chondrocytes – are described below.
- collagen(KAHL-uh-jen): A family of fibrous proteins, collagens are the building blocks of skin, tendon, bone, and other connective tissues.
- proteoglycans(PRO-tee-uh-GLY-kanz): Made up of proteins and sugars, strands of proteoglycans interweave with collagens and form a mesh-like tissue. This allows cartilage to flex and absorb physical shock.
- chondrocytes(KAHN-druh-sytz): Found throughout the cartilage, chondrocytes are cells that produce cartilage and help it stay healthy as it grows. Sometimes, however, they release substances called enzymes that destroy collagen and other proteins. Researchers are trying to learn more about chondrocytes.
How Do You Know if You Have Osteoarthritis?
Usually, osteoarthritis comes on slowly. Early in the disease, your joints may ache after physical work or exercise. Later on, joint pain may become more persistent. You may also experience joint stiffness, particularly when you first wake up in the morning or have been in one position for a long time.
Although osteoarthritis can occur in any joint, most often it affects the hands, knees, hips, and spine (either at the neck or lower back). Different characteristics of the disease can depend on the specific joint(s) affected. For general warning signs of osteoarthritis, see the box on the next page. For information on the joints most often affected by osteoarthritis, please see the following descriptions below:
Hands: Osteoarthritis of the hands seems to have some hereditary characteristics; that is, it runs in families. If your mother or grandmother has or had osteoarthritis in their hands, you’re at greater-than-average risk of having it too. Women are more likely than men to have hand involvement and, for most, it develops after menopause.