Stage 0 OA is classified as “normal” knee health. The knee joint shows no signs of OA and the joint functions without any impairment or pain.
A person with stage 1 OA is showing very minor bone spur growth. Bone spurs are boney growths that often develop where bones meet each other in the joint.
Stage 2 OA of the knee is considered a “mild” stage of the condition. X-rays of knee joints in this stage will reveal greater bone spur growth, but the cartilage is usually still at a healthy size, i.e. the space between the bones is normal, and the bones are not rubbing or scraping one another.
Stage 3 OA is classified as “moderate” OA. In this stage, the cartilage between bones shows obvious damage, and the space between the bones begins to narrow. People with stage 3 OA of the knee are likely to experience frequent pain when walking, running, bending, or kneeling.
Stage 4 OA is considered “severe.” People in stage 4 OA of the knee experience great pain and discomfort when they walk or move the joint.
That’s because the joint space between bones is dramatically reduced—the cartilage is almost completely gone, leaving the joint stiff and possibly immobile. The synovial fluid is decreased dramatically, and it no longer helps reduce the friction among the moving parts of a joint.
Bone realignment surgery, or osteotomy, is one option for people with severe OA of the knee. During this surgery, a surgeon cuts the bone above or below the knee to shorten it, lengthen it, or change its alignment.
Side effects of this surgery include infections at the incision site and blood clots. Recovery from this procedure takes several weeks or months and requires extensive physical and occupational therapy.
It is possible that replacing your arthritic knee won’t be the end of your OA knee problems. You may need additional surgeries or even another knee replacement during your lifetime, but with the newer knees, it may last for decades.