A painful knee can severely affect your ability to lead a full active life. Over the last twenty five years, major advancements in artificial knee replacement have improved the outcome of the surgery greatly. Artificial knee replacement surgery is becoming more and more common.
There are many conditions that can result in degeneration of the knee joint. Osteoarthritis is the most common cause for patients needing to undergo knee replacement surgery. This condition is commonly referred to as "wear and tear arthritis". Osteoarthritis can occur with no previous history of injury to the knee joint - the knee simply "wears out". There may be a genetic tendency in some people that increases their chances of developing osteoarthritis.
The major problem in osteoarthritis is that the cartilage (the articular cartilage) on the surface of the bone inside the joint wears away. This results in bone rubbing against bone, with the slick protective surface of the articular cartilage absent. This causes pain.
Abnormalities of knee joint function resulting from fractures of the knee, torn cartilages and torn ligaments can lead to degeneration many years after the injury. The mechanical abnormality leads to excessive wear and tear.
The symptoms of a degenerative knee joint usually begin as pain while bearing weight on the affected knee. You may limp and the knee may become swollen with fluid. The degeneration can lead to a reduction in the range of motion of the affected knee - the knee bends less than normal and may lose the ability to completely straighten out. Bone spurs will usually develop and can be seen on x-ray. Finally, as the condition becomes worse, the pain may be present all the time and may even keep you awake at night.
The diagnosis of a degenerative knee starts with a history and physical examination. X-rays will be required to determine the extent of the degenerative process and may suggest a cause for the degeneration. Other tests may be required if there is reason to believe that other conditions are contributing to the degenerative process. Blood tests may be required to rule out systemic arthritis (such as Rheumatoid Arthritis) or infection in the knee.
Most degenerative problems will finally require replacement of the painful knee with an artificial knee replacement. The decision to proceed with surgery should be made jointly by you and your surgeon, Dr Allen. You should endeavour to understand as much about the procedure as possible.
Once the decision to proceed with surgery is made, there are several things that may need to be done. You may need to be seen by the anaesthetist prior to your surgery. This is to ensure that you are in the best possible condition to undergo the operation. You may also need to spend time with the Physiotherapist or hospital staff who will be managing your rehabilitation after the surgery. The therapist will sometimes be able to begin the teaching process before the surgery to ensure that you are ready for the rehabilitation afterwards.
As with all major surgical procedures, complications can occur. Some of the most common complications following knee replacement are:
- Thrombophlebitis (DVT)
- Infection
- Stiffness
- Loosening
This is not intended to be a complete list of the possible complications, but these are the most common.
Thrombophlebitis, sometimes called Deep Venous Thrombosis (DVT), can occur after any operation, but is more likely to occur following surgery on the hip, pelvis, or knee. DVT occurs when the blood in the large veins of the leg forms blood clots within the veins. This may cause the leg to swell and become warm to the touch and painful. If the blood clots in the veins break apart, they can travel to the lung, where they get lodged in the capillaries of the lung and cut off the blood supply to a portion of the lung. This is called a pulmonary embolism. (Pulmonary = lung, embolism = fragment of something travelling through the blood system). Surgeons take preventing DVT very seriously. There are many ways to reduce the risk of DVT, but probably the most effective is getting you moving as soon as possible!
Some of the commonly used preventative measures include:
- Pressure stockings to keep the blood in the legs moving.
- Foot pumps that send impulses through the deep veins.
- Medications that thin the blood and prevent blood clots from forming.
****VERY IMPORTANT**** If you have had a previous DVT or Pulmonary Embolism, please make sure you tell the ward staff and the anaesthetist.
Infection can be a very serious complication following an artificial joint replacement. The chance of getting an infection following artificial knee replacement is probably somewhere around 1%. Some infections may show up very early - before you leave the hospital. Others may not become apparent for months, or even years, after the operation. Infection can spread into the artificial joint from other infected areas. You should make sure that you take antibiotics when you have dental work, or have surgical procedures on your bladder and bowel to reduce the risk of spreading germs to the joint.
In some cases, the ability to bend the knee does not return to normal after an artificial knee replacement. You may be put on a CPM machine (Constant Passive Motion) immediately after surgery to try and increase the range of motion following artificial knee replacement or receive physiotherapy beginning soon after the surgery to help regain the motion.
To be able to use the leg effectively to rise from a chair, the knee should bend at least to 90 degrees. A desirable range of motion should be 110 degrees (or greater). Balancing of the ligaments and soft tissues (during surgery) and your movement prior to surgery are the most important determining factors in regaining an adequate range of motion following knee replacement, but sometimes increasing scarring after surgery can lead to an increasingly stiff knee.
The major reason that artificial joints eventually fail continues to be a process of loosening where the metal or cement meets the bone. There have been great advances in extending how long an artificial joint will last, but most will eventually loosen and require a revision. Hopefully, you can expect 12-15 years of service from an artificial knee. In some cases the knee will loosen earlier than that but we hope today’s knees will last even longer! A loose knee is a problem because it causes pain. Once the pain becomes unbearable, another operation will probably be required to revise the knee.
Fracture of the femur or tibia, perforation of the femur or tibia, vascular (blood vessel) complications and nerve problems may occur. These are rare (<1%).
Operation-related death is less than 1 percent in this major operative procedure undertaken in a population that is, for the most part, at middle age or beyond.
Urinary retention (usually in males) and infection (more common in females) may occur. These are treated when and if they arise with usually fairly simple measures.
Pulmonary (lung), cardiovascular (heart conditions and strokes), and gastrointestinal complications are infrequent and usually are related to pre-existing disease. Occasional allergic reactions to drugs and blood can occur.
This list of possible complications may all sound fairly gloomy but the reality is that in the vast majority of cases the benefits of surgery far, far outweigh the possible complications.
Very little of what we do in our daily lives comes without the possibility of injury or physical complications. Surgery is no different. The difference in knee surgery is that we endeavour to help you be as informed as possible so that you may be comfortable in your decision to have surgery and have a realistic approach to it. Overall complications are uncommon and serious complications usually occur in less than 5% of patients, which for the major surgery that this is, is relatively low!
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