Damage can also be caused by rheumatoid arthritis from inflammation of the synovial membrane, which lines the joint. A knee might also be replaced after a traumatic injury to the joint from an accident or sports injury.
The knee is the largest joint in the body, made up of the end of the femur (thigh bone), the top of the tibia (shin bone), and the bone of the kneecap above the femur. The surfaces where these three bones come together to make the joint are also covered with cartilage.
Patients may decide to have a total knee replacement for any of the following reasons:
- Great pain that impedes normal activities like getting up from sitting, walking or climbing stairs
- Great pain while sitting or lying down
- Knee stiffness (difficult to bend or straighten out)
- Deformity in the knee
A knee assessment starts with a physical exam of the patient, including evaluating pain and mobility issues. Usually an X-ray and/or MRI are ordered.
To control knee pain when damage is not serious enough for an operation, non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, can be very effective. Other common treatments are injections into the knee of steroids like cortisone or injections of the lubricant hyaluronic acid.
While a patient at any age may be a candidate for a total knee replacement, doctors prefer patients be in their mid-50s or older since artificial knees can wear out over time and may need to be replaced.
Since the procedure replaces the ends of the bones, it is sometimes referred to as resurfacing the bones. Whether it is called resurfacing or replacement, it is the same procedure.
Today, knee replacements are done mostly on people age 60 to 80. Nevertheless, improvements in the durability and longevity of knee replacement materials have led researchers to estimate that up to 90 percent of artificial knees are still good after 20 years.
Because knee replacement is about improving the quality of life, rather than addressing a life-threatening condition, the operation is always a patient's choice.
The operation is normally done under general anesthesia, though an epidural or spinal injection may be used. During the procedure, the surgeon cuts out damaged tissues, including cartilage and bone from the thigh, shin and kneecap, and then replaces them with an artificial joint made of metal and plastic.
This surgery, minimally invasive for most people, requires an incision of only 4 to 6 inches.
For the great majority of people, knee surgery results in diminishing pain and an increase in knee function. After recovery, activities such as walking, swimming or biking should be possible, although high-impact activities like jogging or tennis may not be.
While complications following knee surgery are rare, care providers do take special measures to prevent infection. Follow-up care includes aggressive physical therapy to help promote mobility and blood flow. Highly motivated patients tend to recover mobility more quickly, often returning to normal activity levels within a few months.
Patients who currently suffer from pain and knee limitations may be good candidates for a total knee replacement. Obesity, end-stage cardiac disease or end-stage pulmonary disease, can be complicating factors for total knee replacement candidates, and the operation may be ruled out entirely.
The best place to start is to get an initial examination by a family physician, who will refer the patient to an orthopedic specialist if needed.
Dr. Roeshot is an orthopedic surgeon with University Orthopedics in State College, Pa. He is on staff at Mount Nittany Medical Center, rated in the top 5 percent of hospitals nationwide for orthopedic surgery. Find more information at www.mountnittany.org/orthopedics.