Knee replacement surgery (also called knee arthroplasty) is an operation performed to alleviate the pain of severe degenerative disease of the knee. This pain is most commonly due to:
Osteoarthritis (wear-and-tear damage of the cartilage)
Inflammatory arthritis (such as rheumatoid arthritis)
Post-traumatic knee arthritis (cartilage damage after a prior fracture near the knee joint or previous ligamentous injury)
Knee replacement involves an incision in the front of the knee through which the damaged cartilage is removed and replaced with a metal implant on the end of the femur (thigh bone) and the top surface of the tibia (shinbone) with a plastic liner in between the metal parts that glides smoothly and takes away the pain previously caused by the rough, damaged cartilage.
Types of knee replacement surgery
Knee replacement surgery may be a total knee replacement or partial/uni-compartmental replacement.
There are three compartments of the knee:
When the cartilage is damaged in two or more compartments, a total knee replacement is done. If the cartilage is only damaged in one compartment, then a partial knee replacement may be an option.
When do you need knee replacement?
Knee replacement is an excellent option to alleviate knee pain due to severe knee arthritis after a course of nonsurgical treatments fail to provide relief. The recommended nonsurgical treatments include:
Physical therapy
Modifying your activities to avoid high-impact running and jumping sports and replacing them with low-impact exercise
Use of nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen)
Cortisone injections in the knee to help the pain
If your knee pain persists after doing nonsurgical treatments and the pain makes it difficult to do your activities of daily living, such as walking, exercising, getting your groceries, doing your job, or climbing up and down stairs, then knee replacement surgery may be the recommended treatment.
Knee replacement surgery benefits
Knee replacement surgery, when done for very severe arthritis as seen on a knee X-ray, is an operation that alleviates pain and restores the function and range of motion of your knee. People can resume an active lifestyle with low-impact activities (such as walking, hiking, riding a bike, playing golf, doubles tennis or pickleball) after knee replacement surgery.
Knee replacement surgery risks
As chief of hip and knee replacement surgery at Boston Medical Center, I’ve found that complications from knee replacement surgery happen less than 1-2% of the time, and most major complications may be avoided. These problems should be addressed before considering knee replacement surgery.
One risk is infection of the metal parts that may result in ongoing pain and the need for more surgery. Infection risk is higher in smokers and patients with obesity and poorly controlled diabetes. Another risk is a blood clot that may travel from the leg to the lung, which may be a life-threatening event.
After surgery, all patients are placed on a blood thinner such as aspirin to reduce the risk for a blood clot. Walking as much as possible leading up to surgery and afterward—including on the same day immediately after surgery—helps to reduce the risk of blood clot. Another risk after knee replacement surgery is knee stiffness and the loss of range of motion. This may happen due to scar tissue forming in the knee. To prevent this, it is important to do physical therapy and daily independent exercises to stretch the knee before surgery and for three months after surgery.
How to prepare for knee replacement surgery
Before knee replacement surgery, it is important to undergo physical therapy to maximize your knee flexibility, strength and balance. Prior to knee replacement surgery, it is also important to lose weight if you live with obesity, quit smoking if you smoke and, if you have diabetes, speak to your doctor to make sure your blood sugars are well controlled.
Another risk for infection after joint replacement is poor dental hygiene. Bacteria may go from your teeth to your bloodstream and travel to the knee implant, causing infection on the metal parts. To prevent this, you must make sure your dental cleanings are up to date within the last 6-12 months.
Prior to surgery, you will be given an antibacterial soap to shower with to reduce bacteria on your skin prior to surgery, which also reduces the risk of serious infection in your knee.
Knee replacement surgery: What to expect
On the day of surgery, you will arrive at the hospital and be given an intravenous (IV) line to receive fluids and medications. To reduce the pain after surgery, it is common to receive a nerve block before you go into the operating room. This helps with pain relief in the first few hours after surgery. Knee replacement surgery is typically done with a spinal anesthesia, which is a less invasive anesthesia that is associated with improved pain relief after surgery as well as less chance of nausea, vomiting and lung problems that may be associated with general anesthesia.
You will not feel anything during the surgery while under the spinal anesthesia. However, in the first few days and weeks after surgery, you may experience pain. To help alleviate this pain, you will be given a combination of medications, including acetaminophen, an anti-inflammatory medication and, if needed, a pain medication, all of which work together to reduce discomfort after knee replacement surgery. Most people are on this combination of medicines for 1-2 weeks after surgery to help with the initial pain.
Knee replacement recovery
After knee replacement surgery, it is very important to walk as much as possible during the recovery. This should start on the same day of surgery to help prevent blood clots. To prevent blood clot, you will also be started on a blood thinner such as aspirin after surgery, which will continue for approximately 4 weeks.
The incision is typically covered with an antibacterial dressing for 7 days and then removed. You can shower directly over this dressing. Typically, immersing the wound in water such as in a bathtub or pool is not recommended until after 4 weeks after the wound is well healed.
You will also start physical therapy immediately after surgery, which will continue for 3 months afterward to improve range of motion, gait and strength.
You will either be discharged from hospital on the same day or the day after knee replacement surgery. People can resume work at a sedentary job in 2 weeks and after 4-12 weeks for a more physically demanding job depending on the amount of walking or lifting required.