Total Knee Arthroplasty – Knee Replacement Surgery
A painful knee can severely affect your ability to lead an enjoyable and active life. There are many conditions that can result in degeneration of the knee joint. Osteoarthritis 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. Common symptoms include stiffness, pain, weakness, and loss of function of the knee. When conservative treatment methods such as medications, physical therapy, and injections fail to provide significant relief, there are surgical options. The most likely option to help over the long term involves that of a knee replacement. Major recent advancements in artificial knee replacement surgery have improved the outcome greatly. Osteoarthritis is the most common reason why patients undergo knee replacement surgery.
Replacing Your Worn Knee
During surgery an incision about 15cm long is made centered over the kneecap. Scarred and contracted muscles are released to allow (in most cases) an improved range of motion. Like a hip or shoulder replacement, surgery involves removing the arthritic surfaces of the knee joint and replacing them with metal and plastic to allow for smoother, more pain-free motion within the joint. The primary goal of the surgery is pain relief. Once the new joint is in place, your surgeon closes the incision with staples or sutures (stitches).
There are two major types of artificial knee replacements:
- A Cemented Prosthesis
- An Uncemented Prosthesis
Both are still widely used. In many cases a combination of the two types are used. The patellar (kneecap) portion of the prosthesis is commonly cemented into place. The choice to use a cemented or uncemented artificial knee is made by your surgeon based on your age, your lifestyle, and need.
Each prosthesis is made up of 4 parts:
The tibial component (bottom portion) replaces the top of the lower bone, the tibia.
The femoral component (top portion) replaces the two femoral condyles and the groove where the patella runs.
The patellar component (kneecap portion) replaces the joint surface on the bottom of the patella that rubs against the femur in the femoral groove.
The tibial tray serves as the menisci.
Typically the femoral component is made of metal. The tibial component is usually made up of two parts – a metal tray that is attached directly to the bone and a plastic spacer that provides the bearing surface. The plastic used is very tough and very slick. A cemented prosthesis is held in place by a type of epoxy cement that attaches the metal to the bone. An uncemented prosthesis has a fine irregular coating or surface that allows bone to grow into it and attach the prosthesis to bone.
It is not known for exactly how long a prosthesis will last, but it can last many years (12-15). This depends on many factors including your health, activity level, quality of the bone, the nature of the disease, and how well the implants adhere to the bone. Knee replacement surgery almost always relieves pain and may give you more strength and movement and may let you return to many of your normal activities.
Hospital stay: The surgical procedure requires the patient to stay in the hospital after the surgery for approximately two to three nights, the patient is then discharged home.
Physical Therapy: You will be started on gentle exercises with the physical therapist on the first day after surgery. You will usually attend physical therapy on an inpatient basis initially to receive ongoing instruction about progression of your exercises. Therapy is then continued on an outpatient basis. These visits are combined with physician office visits while you gradually return to most normal activities over the first few months after surgery. There is significant variability in the speed at which patients recover depending on multiple factors.
Complications:
Stiffness – Postoperative motion may vary depending on the amount of preoperative destruction and contracture that occurred before you had your surgery. To be able to use the leg effectively to rise from a chair, the knee must bend at least to 90 degrees. A desirable range of motion should be greater than 110 degrees. Balancing of the ligaments and soft tissues (during surgery) is the most important determining factor in regaining an adequate range of motion following knee replacement, but sometimes increasing scarring after surgery can lead to an increasingly stiff knee. If this occurs, your surgeon may recommend taking you back to the operating room, placing you under anesthesia once again, and forcefully manipulating the knee to regain motion. This allows the surgeon to breakup and stretch the scar tissue. The goal is to increase the motion in the knee without injuring the joint.
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 blood in a large vein of the leg forms a clot.
Infection – This can be a very serious complication following an artificial joint. 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. Your surgeon may want to make sure that you take antibiotics when you have dental work, or surgical procedures on your bladder and colon to reduce the risk of spreading germs to the joint.
Loosening – 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, but in some cases the knee will loosen earlier than that. A loose prosthesis is a problem because it causes pain. Once the pain becomes unbearable, another operation will probably be required to revise the knee replacement.
Some joints are more prone to stiffness following the surgery, and others are prone to excessive looseness or instability of the joint that in some cases can even lead to dislocation and the need for further treatment. Studies have shown that complications are generally lower in centers that perform this procedure on a regular basis. The overall patient satisfaction with this procedure has been very positive.
Activities: Most patients return to an improved level of function with their daily activities; in some cases, even allowing golf and/or light tennis activities. Heavy weightlifting or heavy labor activities are usually discouraged. This is due to the concern over the prosthesis loosening from the bone over time and thus requiring further surgery.
Antibiotics Before Any Dental Work: You will need to take prophylactic antibiotics before any dental work over the next two years and possibly longer (see: Antibiotic Prophylaxis After Total Joint Replacement handout).