Arthritis is a condition in which the cartilage in the joint because damaged. It can be due to natural wear and tear or due to a problem with the immune system. Because the cartilage provides protection and cushioning for the bones in the joint, arthritic joints may be stiff or painful. Arthritis is commonly graded to describe the extent of the cartilage loss.
Arthritis tends to be measured on a scale of 1-4 (though, since Roman numerals are used, it is actually I-IV). This is so different physicians can read through medical notes and get an idea of the extent of the arthritis. Arthritis is generally measured based on two different systems of measurement, known as the Kellgren system and the Outerbridge system.
The Kellgren system measures arthritis via X-rays and is based on several different features of the joint. One aspect it looks at is joint narrowing. Joint narrowing is a result of their being less cartilage than normal. A normal joint will appear to have space between the bones in the joint. This system also looks for osteophytes, which are small bony pieces at the edge of the joint, as well as sclerosis, which measures the thickening of the bone at the margins of the joint.
According to the Kellgren system, stage I arthritis has little or no joint narrowing and may not even have any osteophytes. Stage II involves minimal joint narrowing and small osteophytes, and stage III has more osteophytes and definite joint narrowing. Stage IV is the most severe stage with multiple large osteophytes being visible on the X-ray. Stage IV arthritis will also have extreme narrowing of the joint so that there is no visible space between the bones on the X-ray, as well as well defined sclerosis.
The Outerbridge scale uses the arthoscopic appearance of the joint to grade arthritis, which means it makes its measurements based on the appearance of the joint when viewed via a small camera placed underneath the skin. Stage IV arthritis on the Outerbridge scale involves the bones being fully exposed on both sides of the joint, essentially meaning that no cartilage is visible. The other levels of arthritis on this scale describe varying degrees of cartilage breakdown. In both systems, stage IV arthritis is indicative of complete "bone on bone" contact, which means that there is no cartilage protecting the bone.
Stage IV Symptoms
The stage of the arthritis on these two scales generally correlates with the severity of the symptoms. That means that a person with stage IV arthritis is more likely to have pain and stiffness of the joint than a person with a lower stage of arthritis. In many cases, people with stage IV arthritis of a joint will need to have the joint replaced because of the lack of cartilage. However, just because a person has stage IV arthritis does not mean that they will have extreme pain or need the joint replaced.