Joint Replacement Surgery
There are several conditions that may lead to your need to consider a knee or hip replacement. One of the most common causes of knee and hip pain is arthritis. Arthritis is a name used to describe a number of diseases or processes (like wear-and-tear) that causes damage to the cartilage. The most common types of arthritis are:
- Osteoarthritis (OA) – sometimes called degenerative arthritis because it is a "wearing out" condition involving the breakdown of cartilage in the joints. When cartilage thins as it wears away, the bones rub against each other, causing pain and stiffness. OA usually occurs in people aged 50 years and older.
- Rheumatoid Arthritis (RA) – results from a disease in which the body’s own immune system attacks the cartilage, and the synovium (a thin layer of tissue that lines the joint space) becomes thickened and inflamed.
- Post-traumatic Arthritis – may develop after an injury to the joint in which the cartilage has been damaged or joint stability compromised.
In an arthritic knee, the worn cartilage no longer cushions the joint, and the knee cannot glide or move smoothly. When the knee is painful, people tend to use it less. Joint pain is made worse by the fact that a person will avoid using a painful joint, weakening the muscles and making the joint even more difficult to move and more painful.
Joint disease, developmental abnormalities and repetitive injuries can also cause enough damage to warrant consideration of a joint replacement.
The New Knee
The knee replacement surgery removes the damaged bone and cartilage from the knee joint and replaces them with artificial joint parts. Those parts are called a prosthesis. The artificial knee provides a smooth surface for your bones to touch and glide over when you move the joint.
The upper part of the artificial knee fits into your thigh bone. The lower part of the artificial knee fits into your shin bone.
Your orthopedic surgeon will remove the damaged cartilage and bone. He will install the new artificial joint surfaces to restore the alignment and function of your knee.
Many different types of designs and materials are used in total knee replacement surgery. They all have three components: the femoral component (made of a highly polished strong metal), the tibial component (made of a durable plastic-like material often held in a metal tray), and the patellar component (also plastic-like).
What can I expect from an artificial knee?
- An artificial knee is not a normal knee.
- The operation should provide pain relief and improved function (compared to your damaged or problem knee) for about ten years. It will not restore completely normal motion; it is likely you will not be able to bend your knee as well as you once could (before you had arthritis or were injured).
- You should be able to do many normal activities.
- Activities that put too much stress on the artificial knee must be avoided.
- It will be difficult to kneel or squat. However, a study was conducted addressing this issue and the results are as follows;
- 100 patients who were at least 6 months following routine uncemented primary total knee were asked to comment on and then asked to demonstrate the ability to kneel. Differences in perceived and actual kneeling ability were noted.
- 32% of patients stated they were able to kneel without significant discomfort. 80% of those that did not kneel stated they avoided this activity because of uncertainties or recommendations from third parties. 64 (64%) of patients were actually able to demonstrate kneeling ability without discomfort or with mild discomfort only. 12 (12%) of the remainder were unable to kneel because of problems that were not related to the knee. 24 (24%) of patients were unable to kneel because of discomfort in the knee.
- There was no difference in the "kneelers" and "non-kneelers" with regard to overall knee score, range of motion and the presence of patella resurfacing.1
- The major long-term problem is loosening of the artificial parts. This occurs because either the cement crumbles (as old mortar in a brick building) or the bone melts away (re-sorbs) from the cement.
- Loosening of the new knee can be because of your body weight and the activities you do.
- Having a second knee operation is not as good as the first, and the risks of complication are higher. This is why knee replacement is not usually done on young patients.