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 is made of these parts:
Cartilage: A hard but slippery coating on the end of each bone, cartilage is the substance that breaks down and wears away in osteoarthritis. It is 65 to 80 percent water, and is made up of these three substances: collagen, proteoglycans, and chondrocytes.
Collagen: A fibrous protein, collagen is the building block of skin, tendon, bone, and other connective tissues.
Proteoglycans: A combination of proteins and sugars, strands of proteoglycans and collagen weave together and form a mesh-like tissue. This allows cartilage to flex and absorb physical shock.
Chondrocytes: Cells that grow all through the cartilage, chondrocytes mainly help cartilage stay healthy and grow. Sometimes, however, they release substances called enzymes that destroy collagen and other proteins. Researchers are trying to learn more about chondrocytes.
Joint capsule: A tough membrane sac that holds all the bones and other joint parts together.
Synovium: 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.
In a healthy joint, the ends of bone are encased in smooth cartilage. Together they are protected by the joint capsule lined with a synovial membrane that produces synovial fluid. The capsule and fluid protect the cartilage, muscles and connective tissues. In a joint 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.
Usually, osteoarthritis comes on slowly. Early in the disease, joints may ache after physical work or exercise. Osteoarthritis can occur in any joint. Most often it occurs at the hands, hips, knees, or spine.
Hands: Osteoarthritis of the fingers is the one type of the disease that seems to be hereditary; that is, it runs in families. More women than men have it, especially after menopause. Small, bony knobs appear on the end joints of the fingers. They are called Heberden’s nodes. Similar knobs (called Bouchard’s nodes) can appear on the middle joints of the fingers. Fingers can become enlarged and gnarled, and may ache or be stiff and numb. The base of the thumb joint is also commonly affected by osteoarthritis. This kind of osteoarthritis can be helped by medications, splints, or heat treatment.
Knees: The knees are the body’s primary weight-bearing joints. For this reason, they are among the joints most commonly affected by osteoarthritis. They may be stiff, swollen, and painful, making it hard to walk, climb, get in and out of chairs, and use bathtubs. If not treated, osteoarthritis in the knees can lead to disability. Medications, losing weight, exercise, and walking aids can reduce pain and disability. In severe cases, knee replacement surgery may be helpful.
Hips: Osteoarthritis in the hip can cause pain, stiffness, and severe disability. People may feel the pain in their hips, or in their groin, inner thigh, or knees. Walking aids such as canes or walkers can reduce stress on the hip. Osteoarthritis in the hip may limit moving and bending. This can make daily activities such as dressing and foot care a challenge. Walking aids, medication, and exercise can help relieve pain and improve motion. The doctor may recommend hip replacement if the pain is severe and not helped by other methods.
Spine: Stiffness and pain in the neck or in the lower back can result from osteoarthritis of the spine. Weakness or numbness of the arms or legs can also result. Some people feel better when they sleep on a firm mattress or sit using back support pillows. Others find help from heat treatment or an exercise program to strengthen the back and abdominal muscles. In severe cases, the doctor may suggest surgery to reduce pain and help restore function.
Osteoarthritis treatment plans often include ways to manage pain and improve function. Such plans can involve exercise, rest and joint care, pain relief, weight control, medications, surgery, and nontraditional treatment approaches. Most successful treatment programs involve a combination of treatments tailored to the patient’s needs, lifestyle, and health.
(Source: National Institute of Arthritis and Musculoskeletal and Skin Diseases)