Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability. It is most commonly performed for osteoarthritis and also 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.
The procedure involves cutting away damaged bone and cartilage from your thighbone, shinbone and kneecap and replacing it with an artificial joint (prosthesis) made of metal alloys, high-grade plastics and polymers.
In determining whether a knee replacement is right for you, an orthopedic surgeon assesses your knee's range of motion, stability and strength. X-rays help determine the extent of damage.
Your doctor can choose from a variety of knee replacement prostheses and surgical techniques, considering your age, weight, activity level, knee size and shape, and overall health.
The operation typically involves substantial postoperative pain, and includes vigorous physical rehabilitation. The recovery period may be 6 weeks or longer and may involve the use of mobility aids (e.g. walking frames, canes, crutches) to enable the patient's return to preoperative mobility.
Risks and complications in knee replacement are similar to those associated with all joint replacements. The most serious complication is infection of the joint, which occurs in <1% of patients. Risk factors for infection are related to both patient and surgical factors. Deep vein thrombosis occurs in up to 15% of patients, and is symptomatic in 2–3%. Nerve injuries occur in 1–2% of patients. Persistent pain or stiffness occurs in 8–23% of patients. Prosthesis failure occurs in approximately 2% of patients at 5 years.
There is increased risk of complications for obese people going through total knee replacement. The morbidly obese should be advised to lose weight before surgery and, if medically eligible, would probably benefit from bariatric surgery.
Fracturing or chipping of the polyethylene platform between the femoral and tibial components may be of concern. These fragments may become lodged in the knee and create pain or may move to other parts of the body. Advancements in implant design have greatly reduced these issues but the potential for concern is still present over the lifespan of the knee replacement.
Preparing for Surgery
If you decide to have total knee replacement surgery, your orthopaedic surgeon may ask you to schedule a complete physical examination with your family physician several weeks before the operation. This is needed to make sure you are healthy enough to have the surgery and complete the recovery process. Many patients with chronic medical conditions, like heart disease, may also be evaluated by a specialist, such as a cardiologist, before the surgery.
Several tests, such as blood and urine samples, and an electrocardiogram, may be needed to help your orthopaedic surgeon plan your surgery.
Tell your orthopaedic surgeon about the medications you are taking. He or she will tell you which medications you should stop taking and which you should continue to take before surgery.
Although the incidence of infection after knee replacement is very low, an infection can occur if bacteria enter your bloodstream. To reduce the risk of infection, major dental procedures (such as tooth extractions and periodontal work) should be completed before your total knee replacement surgery.
People with a history of recent or frequent urinary infections should have a urological evaluation before surgery. Older men with prostate disease should consider completing required treatment before undertaking knee replacement surgery.
Although you will be able to walk on crutches or a walker soon after surgery, you will need help for several weeks with such tasks as cooking, shopping, bathing, and doing laundry.
Several modifications can make your home easier to navigate during your recovery. The following items may help with daily activities:
• Safety bars or a secure handrail in your shower or bath
• Secure handrails along your stairways
• A stable chair for your early recovery with a firm seat cushion (and a height of 18 to 20 inches), a firm back, two arms, and a footstool for intermittent leg elevation
• A toilet seat riser with arms, if you have a low toilet
• A stable shower bench or chair for bathing
• Removing all loose carpets and cords
• A temporary living space on the same floor because walking up or down stairs will be more difficult during your early recovery
Your Hospital Stay
You will most likely stay in the hospital for several days.
After surgery, you will feel some pain. This is a natural part of the healing process. Your doctor and nurses will work to reduce your pain, which can help you recover from surgery faster.
Medications are often prescribed for short-term pain relief after surgery. Many types of medicines are available to help manage pain, including opioids, non-steroidal anti-inflammatory drugs (NSAIDs), and local anesthetics. Your doctor may use a combination of these medications to improve pain relief, as well as minimize the need for opioids.
Be aware that although opioids help relieve pain after surgery, they are a narcotic and can be addictive. Opioid dependency and overdose has become a critical public health issue in the U.S. It is important to use opioids only as directed by your doctor. As soon as your pain begins to improve, stop taking opioids. Talk to your doctor if your pain has not begun to improve within a few days of your surgery.
Blood Clot Prevention
Your orthopaedic surgeon may prescribe one or more measures to prevent blood clots and decrease leg swelling. These may include special support hose, inflatable leg coverings (compression boots), and blood thinners.
Foot and ankle movement also is encouraged immediately following surgery to increase blood flow in your leg muscles to help prevent leg swelling and blood clots.
Most patients begin exercising their knee the day after surgery. In some cases, patients begin moving their knee on the actual day of surgery. A physical therapist will teach you specific exercises to strengthen your leg and restore knee movement to allow walking and other normal daily activities soon after your surgery.
To restore movement in your knee and leg, your surgeon may use a knee support that slowly moves your knee while you are in bed. The device is called a continuous passive motion (CPM) exercise machine. Some surgeons believe that a CPM machine decreases leg swelling by elevating your leg and improves your blood circulation by moving the muscles of your leg.
It is common for patients to have shallow breathing in the early postoperative period. This is usually due to the effects of anesthesia, pain medications, and increased time spent in bed. This shallow breathing can lead to a partial collapse of the lungs (termed "atelectasis") which can make patients susceptible to pneumonia. To help prevent this, it is important to take frequent deep breaths. Your nurse may provide a simple breathing apparatus called a spirometer to encourage you to take deep breaths.
Your Recovery at Home
The success of your surgery will depend largely on how well you follow your orthopaedic surgeon's instructions at home during the first few weeks after surgery.
You will have stitches or staples running along your wound or a suture beneath your skin on the front of your knee. The stitches or staples will be removed several weeks after surgery. A suture beneath your skin will not require removal.
Avoid soaking the wound in water until it has thoroughly sealed and dried. You may continue to bandage the wound to prevent irritation from clothing or support stockings.
Some loss of appetite is common for several weeks after surgery. A balanced diet, often with an iron supplement, is important to help your wound heal and to restore muscle strength.
Exercise is a critical component of home care, particularly during the first few weeks after surgery. You should be able to resume most normal activities of daily living within 3 to 6 weeks following surgery. Some pain with activity and at night is common for several weeks after surgery.
Your activity program should include:
• A graduated walking program to slowly increase your mobility, initially in your home and later outside
• Resuming other normal household activities, such as sitting, standing, and climbing stairs
• Specific exercises several times a day to restore movement and strengthen your knee. You probably will be able to perform the exercises without help, but you may have a physical therapist help you at home or in a therapy center the first few weeks after surgery.
You will most likely be able to resume driving when your knee bends enough that you can enter and sit comfortably in your car, and when your muscle control provides adequate reaction time for braking and acceleration. Most people resume driving approximately 4 to 6 weeks after surgery.
Avoiding Problems After Surgery
Blood Clot Prevention
Follow your orthopaedic surgeon's instructions carefully to reduce the risk of blood clots developing during the first several weeks of your recovery. He or she may recommend that you continue taking the blood thinning medication you started in the hospital. Notify your doctor immediately if you develop any of the following warning signs.
Warning signs of blood clots.
The warning signs of possible blood clots in your leg include:
• Increasing pain in your calf
• Tenderness or redness above or below your knee
• New or increasing swelling in your calf, ankle, and foot
Warning signs of pulmonary embolism. The warning signs that a blood clot has traveled to your lung include:
• Sudden shortness of breath
• Sudden onset of chest pain
• Localized chest pain with coughing
A common cause of infection following total knee replacement surgery is from bacteria that enter the bloodstream during dental procedures, urinary tract infections, or skin infections. These bacteria can lodge around your knee replacement and cause an infection.
After knee replacement, patients with certain risk factors may need to take antibiotics prior to dental work, including dental cleanings, or before any surgical procedure that could allow bacteria to enter the bloodstream. Your orthopaedic surgeon will discuss with you whether taking preventive antibiotics before dental procedures is needed in your situation.
Warning signs of infection. Notify your doctor immediately if you develop any of the following signs of a possible knee replacement infection:
• Persistent fever (higher than 100°F orally)
• Shaking chills
• Increasing redness, tenderness, or swelling of the knee wound
• Drainage from the knee wound
• Increasing knee pain with both activity and rest
A fall during the first few weeks after surgery can damage your new knee and may result in a need for further surgery. Stairs are a particular hazard until your knee is strong and mobile. You should use a cane, crutches, a walker, hand rails, or have someone to help you until you have improved your balance, flexibility, and strength.
Your surgeon and physical therapist will help you decide what assistive aides will be required following surgery and when those aides can safely be discontinued.
For most people, knee replacement provides pain relief, improved mobility and a better quality of life. And most knee replacements can be expected to last more than 15 years.
Three to six weeks after surgery, you generally can resume most daily activities, such as shopping and light housekeeping. Driving is also possible at around three weeks if you can bend your knee far enough to sit in a car, if you have enough muscle control to operate the brakes and accelerator, and if you're not still taking narcotic pain medications.
After recovery, you can engage in various low-impact activities, such as walking, swimming, golfing or biking. But you should avoid higher impact activities — such as jogging, skiing, tennis and sports that involve contact or jumping. Talk to your doctor about your limitations.