Knee replacement, or knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve the pain and disability of osteoarthritis. It may be performed for other knee diseases such as rheumatoid arthritis and psoriatic arthritis. In patients with severe deformity from advanced rheumatoid arthritis, trauma, or long standing osteoarthritis, the surgery may be more complicated and carry higher risk. Osteoporosis does not typically cause knee pain, deformity, or inflammation and is not a reason to perform knee replacement.
Other major causes of debilitating pain include meniscus tears, cartilage defects, and ligament tears. Debilitating pain from osteoarthritis is much more common in the elderly.
Knee replacement surgery can be performed as a partial or a total knee replacement. In general, the surgery consists of replacing the diseased or damaged joint surfaces of the knee with metal and plastic components shaped to allow continued motion of the knee.
The operation involves substantial postoperative pain, and includes vigorous physical rehabilitation. The recovery period is 6 weeks or longer and involves use of a walker and then a cane.
What is a total knee replacement?
A total knee replacement is a surgical procedure whereby the diseased knee joint is replaced with artificial material. The knee is a hinge joint which provides motion at the point where the thigh meets the lower leg. The thigh bone (or femur) abuts the large bone of the lower leg (tibia) at the knee joint. During a total knee replacement, the end of the femur bone is removed and replaced with a metal shell. The end of the lower leg bone (tibia) is also removed and replaced with a channeled plastic piece with a metal stem. Depending on the condition of the kneecap portion of the knee joint, a plastic “button” may also be added under the kneecap surface.
The posterior cruciate ligament is a tissue that normally stabilizes each side of the knee joint so that the lower leg cannot slide backward in relation to the thigh bone. In total knee replacement surgery, this ligament is either retained, sacrificed, or substituted by a polyethylene post. Each of these various designs of total knee replacement has its benefits and risks.
Total Knee Replacement
Total knee replacement (arthroplasty) has proven to be a very effective surgical treatment of osteoarthritis of the knee for many years. Relatively recently, however, partial knee replacement (also known as unicondylar knee replacement) has emerged as a possible – and viable – option for certain patients.
For the treatment of end stage arthritis of the knee, total knee replacement is a very predictable surgery with an excellent outcome. It promises a return to activities of daily living, walking, and a life with no (or minimal) pain. The results for total knee arthroplasty over the last 20 years have shown continuous improvement in knee function as well as durability of the surgery, and most patients today can expect a ten year implant survival rate in the range of 95% and a 20 year survival rate in the range of 85% – 90%. This means that 20 years after surgery, nine out of ten patients will still have a functioning implant and will not need another surgery. These promising outcomes have resulted in the widespread use of total knee arthroplasty for the treatment of osteoarthritis of the knee.
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What is the benefit of the partial knee replacement?
Smaller Incision
A traditional knee replacement surgery involves an incision about 8 inches over the front of the knee. There is more significant dissection necessary to complete the procedure compared to the unicompartmental knee surgery. In the minimally invasive partial knee replacement, the incision is about 3 inches, and the amount of dissection and bone removal is much smaller.
Less Blood Loss
Because of the extent of dissection and bone removal necessary for a total knee replacement, the need for a blood transfusion is relatively common. With the unicompartmental knee procedure, a blood transfusion is infrequently needed, and patients do not need to consider giving blood preoperatively.
Shorter Recovery
Both the time in hospital and the time to functional recovery are less with the partial knee replacement. Patients are known to have been discharged on the day of the procedure, although most often patients are discharged on the first or second post-operative day. With traditional total knee replacement, patients seldom leave before three or four days in the hospital, and often require a stay in an in-patient rehabilitation unit.