I am 60 and was diagnosed with knee osteoarthritis five years ago. Each year I have an X-ray. The last X-ray led my doctor to recommend a knee replacement. What do you look for on X-rays to make someone a candidate for surgery?

Osteoarthritis is the wear-and-tear type of arthritis, with specific X-ray findings used to determine the severity of disease. This information, the history of disabling symptoms, as well as the examination determine need for surgery. As the arthritis advances, the cartilage on the ends of the two bones forming the joint wears. This is reflected by a narrowing of the joint space on an X-ray.
Bone spurs called osteophytes are bony projections that emerge from the edges of the joint margin. The osteophytes can be imaged on X-rays and are a marker for the degree of arthritic changes. Thinning of the joint cartilage weakens ability to absorb shock. Thus, the
bone just under the cartilage becomes denser because of added stress. Increased bone density at the joint line can be seen on an X-ray and is a feature of advancing osteoarthritis. Cysts in bones surrounding the joint line are common, but not a unique feature of osteoarthritis. These findings can be seen as clear spaces in the bone adjacent to the joint line on an X-ray. It is important to remember that X-rays do not always mirror the degree of symptoms one experiences with osteoarthritis. Diagnosis is primarily done by history-taking and physical exam.