What is Osteoarthritis?

Joints are composed of numerous structures. When a joint is affected by osteoarthritis, all of these structures may be affected in varying degrees. This accounts for the many changes that occur in osteoarthritic joints. By knowing these changes, you can better understand your doctor’s recommendations.

Joints Have Many Functions

• Our joints enable us to move. We carry out many thousands of movements every day, most of them unconsciously. The joints are naturally lubricated to improve and facilitate these movements. The lubricant consists of a fluid film secreted by the mucous membranes lining the interior of the joints.

• Joints have a shock absorber to cushion sudden, hard movements; the joint cartilage. This smooth, resilient coating protects the joints during movements and allows movements to progress in a normal pattern.

• Joints provide stability. Joints have important structures that guide certain movements and prohibit others. For example, the joint in the fingertip can move only like a hinge. It does not permit side-to-side movements. The joint is protected against “wrong” movements. This protection is provided by portions of the joint capsule (called the “fibrous capsule”) and the ligaments that “bind” the joint together.

What are the stages in the development of osteoarthritis, and what exactly is osteoarthritis?

• Early Stage

Osteoarthritis always starts with damage to the cartilage that covers the joint surfaces. At first, this cartilage damage is often limited to a small area of perhaps half a square inch. Also, the damage is still superficial. Within a short time, x-ray films of the joint show an increase in the density of the bone. This always occurs in bone areas that are located directly beneath the diseased cartilage. These additional changes in the bone are a critical sign that early-stage osteoarthritis has developed. Without the changes to the bone, there is only “cartilage damage,” but no “osteoarthritis.” Therefore, osteoarthritis always means cartilage damage with changes to the bone.

• Late Stage

Many years may separate “early stage” and “late stage” osteoarthritis. Therefore, most osteoarthritis patients find themselves somewhere in between. The changes to their joints are more pronounced than in the early stage, but still less than in the late stage.

In the late stage, the joint cartilage in the diseased area is not only diseased and damaged, but completely eroded and worn away. Without that protective covering, opposite bones rub directly against each other. This is also called “bone-to-bone contact”. X-rays of late stage osteoarthritis show the absence of normal cartilage and exhibit direct contact between bones.

The bone itself has also changed in relation to the early stage:

• X-rays clearly show them to be denser and harder.
• The joints have developed large bony jagged edges. These bony outgrowths (“osteophytes”) broaden the entire joint. The resulting deformity is outwardly apparent to the patient. The affected joints appear larger and expanded. Bony spurs can also touch each other during certain movements, causing additional pain.

Causes and Consequences of Osteoarthritis

As described above, osteoarthritis begins with cartilage damage. Hundreds, if not thousands of different factors can cause cartilage damage. The most common causes are accidents, carrying heavy loads over an extended period of time, congenital deformities of the joints, metabolic disorders, and presumably, poor nutrition.

The consequences of osteoarthritis are known too well by those it afflicts:

–– Pain

–– Inflammation

–– Thickening and Deformity

–– Stiffness

However, the severity and combination of these symptoms varies with each patient.

Note: Not all joints are endangered in the same way or by the same factors. Due to the numerous causes of cartilage damage unique to each joint, we’ll discuss the risk factors for specific joints in more detail in upcoming issues of ARTHRITIS INFO. We will also give practical advice on what can be done about osteoarthritis of the hands, hips, and other joints.