The knee is the largest joint in the body. It is commonly referred to as a “hinge” joint because it allows the knee to flex and extend. While hinges can only bend and straighten, the knee has the additional ability to rotate (turn) and translate (glide). The knee joint is formed by the tibia (shin bone), the femur (thigh bone) and the patella (knee cap).
Each bone end is covered with a layer of smooth shiny cartilage that cushions and protects while allowing near frictionless movement. Cartilage, which contains no nerve endings or blood supply, receives nutrients from the fluid contained within the joint.
Surrounding the knee structure is the synovial lining, which produces this moisturizing lubricant. If damaged, the cartilage is not capable of repairing itself. Tough fibers, called ligaments, link the bones of the knee joint and hold them in place while adding stability and elasticity for movement. Muscles and tendons also play an important role in keeping the knee joint stable and mobile.
What Causes Knee Pain
The largest cause of knee pain is arthritis. Three common types of arthritis can result in joint damage: osteoarthritis, rheumatoid arthritis, and trauma-related arthritis. Osteoarthritis, most common in people over sixty, is a disease which affects the tissues that allow joints move smoothly. The layers of cartilage and synovium become damaged and, as they wear away, the bones are left unprotected to rub against each other. With rheumatoid arthritis, the body’s immune system produces a chemical which targets and then destroys the synovial lining, the cartilage, and joint surface also resulting in joint pain and loss of mobility. This disease can affect any age group, however females more often than males. In the third group, arthritis is developed in a joint which sustained trauma and also results in joint damage, pain, and loss of mobility.
Total Knee Replacement
When conservative treatments fail to provide adequate relief to knee pain, a total knee replacement is considered. This surgical procedure consists of using three artificial components to replace the joint. The femoral (thigh) component is made of metal and covers the end of the thigh bone. It is either cemented to the bone or inserted for the tissues to grow into the porous coating of the device. The tibial (shin bone) component is made of metal and polyethylene, a medical plastic, and covers the end of the bone and is secured by either of the same methods used for the femoral component. Lastly, the patella (knee cap) is inserted with cement and is of all polyethylene.
During surgery, these three components are inserted through an incision that runs three or four inches above the knee down over of the kneecap to several inches below the knee. The new components are stabilized by the existing ligaments and muscles. Sutures or staples are used to close the incision and are removed two weeks following surgery.
Preparing for Surgery
It may be necessary for an additional medical evaluation by your own family physician depending on any preexisting health conditions. If you are a smoker, it is advisable for you to stop two weeks prior to surgery. This will help your knee to recover faster. Certain medications may also be stopped two weeks before surgery as advised by the surgeon. Patients in good health may be asked to donate one unit of their blood to be used following surgery if necessary.
Knee Surgery Animation»
After midnight on the night prior to your surgery, you cannot eat or drink anything.
What To Expect After Surgery
A plastic drain will be coming through the surgical dressing to remove any blood that accumulates in the surgical area. This blood is collected and during the first 6 hrs and can be filtered and reinfused back into your body via your IV. After 6hrs, the blood is collected, but not reinfused. The drain will probably be removed on the second day after surgery. The dressing will also be changed and a smaller one applied.
An “immobilizer” (a cloth support with stays) will fit around this dressing and will hold your leg straight when walking or sitting in a chair. A “Continuous Passive Motion” (CPM) machine will be used while in bed. In this machine your leg is held softly in acradle, and the knee is then gently and slowly bent and straightened.
An IV may remain in your arm for several days to administer antibiotics or other medications you may need. This helps prevent infection and gives you proper nourishment until you are eating and drinking comfortably. You will begin regular fluid and food intake under the direction and advice of your surgeon. You may be given a “pain pump” or PCA-patient controlled anesthesia pump for the first 1 to 2 days after surgery (see Medication/Pain Control below).
After the acute pain has diminished, usually the day after surgery, a physical therapist will help you begin standing and walking again. If cement has been used, a walker or crutches will be required for three to four weeks followed by three to four weeks with a cane. If cement has not been used, a walker or crutches will be required for four to six weeks followed by four to six weeks with a cane.
Most patients can return home four to ten days following surgery.
Your knee rehabilitation program will begin the day after surgery and are monitored by a physical therapist. Exercises will be demonstrated that need to be done each day.
It is normal for you to have some discomfort. You may be given a “pain pump” or PCA-patient controlled anesthesia pump for the first 1-2 days after surgery. This device delivers pain medicine into your IV when you want it. You push a button and the medicine is delivered (usually morphine or Demerol). Your surgeon orders the pump set so that you only receive the appropriate amount of medicine needed. The pump is usually set to deliver medicine up to every 8 minutes. Or if you don’t want to bother with pushing the button, the pump can be set to deliver medicine automatically on a set schedule determined by your doctor. As soon as you are eating well, your doctor will switch from IV medicine to pain pills that you take by mouth. This is usually done on the first or second day after surgery. You will receive a prescription for pain medication before leaving the hospital.
Prior to your discharge instructions for what to do at home will be given. Adhere to all precautions until your follow-up visit ten to fourteen days following surgery.
If you see any of the following, contact your surgeon immediately: drainage and/or foul odor coming from the incision, fever of 101 degrees or higher for two days, or increased swelling, tenderness, redness, and/or pain.
Returning to a sedentary or office job may be possible as soon as three to six weeks following surgery. A job requiring prolonged walking, standing, or lifting may need a full three months of recovery first. Some types of work, such as construction, may not be advised with your new knee.
After three months, general walking, riding a bicycle, and swimming are encouraged physical activities. Dancing, golf, and bowling are also permitted. Vigorous sports such as any contact sports, running, racquet sports, and skiing are not recommended at any time because it puts too much stress on the new knee.
Driving is usually possible once full weight-bearing on the leg is achieved. This usually occurs by six weeks.
Follow-up to remove sutures or staples will be scheduled for ten to fourteen days following surgery. Another follow-up to see progress will be scheduled four to six weeks following surgery. Other follow-ups, which may continue for as long as a year after surgery, will be scheduled depending on progress.
Alert your dentist that you have a knee replacement before any surgical work. Because bacteria can enter the blood stream and cause an infection, antibiotics will need to be prescribed before the procedure.