When debilitating pain, accompanied by stiffness, swelling and limited motion in your knee keep you from your daily activities, it may be time to consider total knee replacement. The development of total knee replacement technology began more than 30 years ago. Each year, more than 500,000 people in the United States undergo knee replacement surgery to help ease pain and stiffness and restore mobility
The most frequent cause of discomfort and chronic knee pain is arthritis, which is the leading cause of disability in the United States. In fact, it’s estimated that 1 in 5 people in the United States has arthritis, and two-thirds are under the age of 65
Of the more than 100 types of arthritis, the following three are the most common causes of joint damage:
Osteoarthritis is a disease that involves the breakdown of tissues that allow joints to move smoothly. The layers of cartilage and synovium become damaged and wear away, leaving the underlying bones unprotected from rubbing against each other.
Rheumatoid arthritis is a systemic disease because it may attack any or all joints in the body. It affects women more often than men and can strike young and old alike. With rheumatoid arthritis, the body’s immune system produces a chemical that attacks and destroys the synovial lining covering the joint capsule, the protective cartilage and the joint surface, causing pain, swelling, joint damage and loss of mobility.
Trauma-related arthritis, which results when the joint is injured, is the third most common form of arthritis. It also causes joint damage, pain and loss of mobility.
The knee is the largest joint in the body. It is commonly referred to as a “hinge” joint because it allows the knee to flex and extend. While hinges can only bend and straighten, the knee has the additional ability to rotate (turn) and translate (glide).
The knee joint is formed by the shin bone (tibia), the thigh bone (femur) and the kneecap (patella). The end of each bone is covered with a layer of slick cartilage, which cushions and protects the bone while allowing smooth movement. If damaged, the cartilage cannot repair itself.
Tough fibers, called ligaments, connect the bones of the knee joint and hold them in place, adding stability and elasticity for movement. Muscles and tendons also play an important role in keeping the knee joint stable and mobile.
When medications, physical therapy and other conservative methods of treatment no longer relieve pain, total knee replacement surgery may be considered. Your surgeon will help you decide if the pain and loss of movement is severe enough that you should undergo the procedure.
Your orthopaedic surgeon can replace your arthritic knee with total knee implants, which have been shown to provide long-term relief.
In general, 90% to 95% of patients are satisfied with the outcome of their total knee replacement, and in some designs, 95% of the knee replacements are still in use after 10 to 15 years.
In total knee replacement (or arthroplasty), the diseased surfaces of the bones are replaced with implants called prostheses.
The femoral (thigh) component is made of metal and covers the end of the thigh bone.
The tibial (shin bone) component is made up of both metal and polyethylene (medical-grade plastic) parts that cover the top end of the tibia. The metal forms the base of this component, while the polyethylene is attached to the top of the metal. That polyethylene “insert” serves as a cushion–a smooth gliding surface between the two metal components (see illustration).
The third component, the patella or kneecap, may be all polyethylene or a combination of metal and polyethylene.
The components may be cemented to the bone or, in some cases, inserted without cement to allow bone tissues to grow into the three-dimensional porous coating of the device.
The total knee replacement is inserted through an incision and the new components are stabilized by your ligaments and muscles, just as they are in your natural knee.
Your knee evaluation will begin with a detailed questionnaire. Your medical history is very important in determining whether surgery is necessary and medically safe. It helps the surgeon understand your pain, limitations in activity and the progression of your knee problem.
After your history is taken, a physical exam is performed. The range of motion of your knee is measured, your legs are evaluated for conditions such as bowlegs or knock-knees, and your muscle strength is analyzed. The surgeon will observe how you walk, sit, bend and move. X-rays will be taken of your knee joint.
A small amount of fluid may be taken from your knee joint to check for infection.
After your initial orthopaedic evaluation, the surgeon will discuss all possible alternatives to surgery. If the X-rays show severe joint damage and no other means of treatment has provided relief, total knee replacement surgery may be recommended.
To prepare yourself for surgery, you may be asked to do a number of things, including lose weight and/or stop smoking (if applicable). It is essential that you tell your surgeon about any medications or supplements you are taking. Bring a list of all medications and dosages, including over-thecounter medications to your appointment. Your doctor may want you to donate your own blood ahead of time for a possible transfusion during surgery.
It is normal to feel pain and discomfort after surgery. Be sure to inform the nurse of your pain.
Your leg will be supported and elevated on one or two pillows to help your circulation and stretch your muscles. Under the direction of your surgeon, you will be asked to move your ankle to promote circulation and prevent stiffness in your ankle joint.
The nurse will help you find comfortable positions and encourage you to do the ankle exercises.
After 24 hours, you should begin to drink fluids regularly, according to your surgeon’s directions.