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A painful knee can severely affect a patient’s ability to lead a full, active life. Over the last 25 years, major advancements in the artificial knee replacement procedure have greatly improved the outcome of surgery. Artificial knee replacement surgery is becoming more and more common as the population of the world begins to age.

Causes For Knee Joint Replacement

Knee DegenerationThere are many conditions that result in degeneration of the knee joint. Osteoarthritis is the most common reason patients have a knee replacement surgery and is commonly referred to as “wear and tear arthritis”. Osteoarthritis can occur with no previous injury to the knee joint – the knee simply “wears out”. Some people may have a genetic tendency that increases their chances of developing osteoarthritis.

Osteoarthritis causes the cartilage on the surface of the bone, inside the joint, to wear away. Once the slick protective surface of the articular cartilage is worn away, the results are bone rubbing against bone. Bone rubbing against bone is painful.

Fractures of the knee, torn cartilage, and torn ligaments can cause the knee joint to function abnormally. This abnormal function can lead to excessive wear and tear of the joint many years after the injury – just like an out-of-balance tire can wear out too soon.

Knee Degeneration


The symptoms of a degenerative knee joint usually begin as pain while bearing weight on the affected knee, such as when walking. You may start to limp and the knee may become swollen with fluid. The range of motion of the affected knee can also be affected, which means the knee will bend less than normal and may lose its ability to completely straighten out. Bone spurs will usually develop and can be seen on x-ray. Finally, as the condition worsens, one may feel pain may almost all of the time. Pain may even keep the patient awake at night.


The diagnosis of a degenerative knee joint starts with a complete history and physical examination by the surgeon. X-rays are required to determine the degree of arthritis within the knee joint, and may help suggest a cause for the degeneration in the knee. Different tests may be required if the surgeon thinks other conditions may be adding to the degenerative process. Blood tests can rule out systemic arthritis, such as rheumatoid arthritis, or an infection in the knee.

Medical Treatment

Not all degenerative knee conditions require a knee replacement as an initial treatment. The doctor may suggest several alternative treatments to avoid replacing the knee as long as possible. Using a cane may help relieve some of the pain and allow the patient to walk more comfortably. Anti-inflammatory medicines may reduce the inflammation from the arthritis and reduce pain.


Most degenerative problems will eventually require replacement of the painful knee with an artificial knee joint, called a prosthesis. Once the decision to have surgery is made, there are several things that need to be done. The hospital and orthopedic surgeon will require the patient to have a complete physical with his or her primary care doctor. This is to ensure the patient is in the best possible condition to undergo the operation. The patient may also need to spend time with the physical therapist who will be managing the rehabilitation after the surgery. The therapist will begin the teaching process before the surgery to ensure the patient is ready for the rehabilitation afterwards.

One purpose of the pre-operative visit with the physical therapists is to record baseline information. This includes measurements of the current pain levels, what the patient is able to do, how much swelling he or she has in the knee, and the amount of movement and strength of each knee.

Another reason the pre-operative visit is helpful is to help the patient prepare for the rehabilitation after surgery. The patient will begin practicing some of the exercises he or she will use right after surgery. He or she will also be trained to use a walker or crutches. Whether or not the surgeon uses a cemented or non-cemented type knee prosthesis will determine how much weight the patient will be able to place on his or her foot while walking. Finally, an assessment will be made to see if the patient has any special needs once they return home.

The Artificial Knee Joint, Called a Prosthesis

There are two main types of artificial knee replacements:

  • Cemented Prosthesis
  • Uncemented Prosthesis

A cemented prosthesis is held in place using an epoxy-type cement that attaches the metal to the bone.

An uncemented prosthesis has a fine mesh of holes on the surface that allows the bone to grow into the mesh and attaches the prosthesis to the bone.

Knee Cemented vs. Uncemented

A cemented prosthesis is held in place using an epoxy type cement that attaches the metal to the bone.

An uncemented prosthesis has a fine mesh of holes on the surface that allows the bone to grow into the mesh and attaches the prosthesis to the bone.

Both types are widely used. In many cases, a combination of the two types is used. The kneecap, or patellar, portion of the prosthesis is usually cemented into place. The choice to use a cemented or uncemented prosthesis is based on the patient’s age and lifestyle.

Artificial Knee Joint Components

Each prosthesis has four parts:

  • The tibial component replaces the end of the tibia. The tibia is commonly called the shinbone.
  • The femoral component replaces the end of the femur, the groove where the kneecap slides. The femur is commonly called the thighbone. It is the largest bone in the body.
  • The patellar component replaces the surface on bottom of the patella. The “top” of the kneecap is the part you can feel through the skin. The “bottom” is the on the other side, and slides up and down in the femoral groove, whenever the leg is bent or straightened.

The femoral component is made of metal. The tibial component is usually made of two parts – a metal tray that is fitted directly onto the bone, and a plastic spacer that provides a bearing surface. The plastic used is very tough and very slick – so slick and tough that one could ice skate on a sheet of the plastic without much damage to the plastic.

The Operation

Replacing the knee begins with making an incision on the front of the knee to allow access to the knee joint.

Total Knee Replacement - Preparing the Femur

Shaping the Distal Femoral Bone

Once the knee joint is entered, a special cutting tool is placed on the end of the femur. This special tool ensures the bone is cut while keeping the proper alignment to the leg’s original angles – even if the arthritis has made the leg bowlegged or knock-kneed. Several pieces of diseased bone are cut away from the end of the femur so the artificial knee can be attached.

Total Knee Replacement - Preparing the Tibia

Preparing the Tibial Bone

Then the top of the tibia is cut using another cutting tool that also ensures proper alignment.

Total Knee Replacement - Preparing the Patella

Preparing the Patella

The undersurface of the kneecap is removed.

Total Knee Replacement - Knee Shaping

Frontal View

This is what the prepared surfaces look like viewed from the front. The patella has been moved to allow the knee to be seen.

Total Knee Replacement - Placing the Femoral Component

Placing the Femoral Component

The femoral component is then fit on the femur. In the uncemented type of femoral component, the prosthesis is held on the end of the bone because the end of bone has a tapered cut. The metal prosthesis is made to almost exactly match the tapered cut of the bone. Fitting the femoral component onto the end of the bone holds the component in place by friction. In the cemented component, epoxy cement is used to attach the metal prosthesis to the bone.

Total Knee Replacement - Placing the Tibial Component (Metal Tray)

Placing the Tibial Component (metal tray)

The metal tray that holds the plastic spacer is attached to the end of the tibia. The metal tray is either cemented into place, or held in place with screws if the component is the uncemented type. The screws hold the tray in place until the bone grows into the porous coating. The screws are left in the bone and are not removed.

Total Knee Replacement - Placing the Tibial Component (Plastic Spacer)

Placing the Tibial Component (plastic spacer)

The plastic spacer is attached to the metal tray of the tibial component. If the plastic spacer wears out it can be replaced if the rest of the prosthesis is in good condition – a so called retread.

Total Knee Replacement - Placing the Patellar Component

Placing the Patellar Component

The patellar button is usually cemented into place behind the patella.

Completed Knee Replacement

The Completed Knee Replacement

X-ray from the side compared with illustration of knee prosthesis.

Completed Knee Replacement - X-Ray Side View

X-ray from the front compared with illustration of knee prosthesis.

Completed Knee Replacement - X-Ray Front View


While the patient is in the hospital:

  • Range of Motion exercises
  • Walking
  • Exercises for strength and flexibility

The first physical therapy visit will take place shortly after surgery. Therapy will focus on the range of motion in the knee and gentle movement will be used to help begin bending and straightening of the knee. If we recommend a continuous passive motion (CPM) machine, it will be adjusted for the knee. When the patient is stabilized, the therapist will assist him or her for a short walk using crutches or a walker. Physical therapy will continue once or twice a day. The patient will be discharged home when he or she can safely:

  • get into and out of bed,
  • walk up to 75 feet with crutches or a walker,
  • go up and down a flight of stairs, and
  • get to the bathroom.

It is also important for the patient to have good contraction of the upper thigh muscle, called the quadriceps, as well as an increase of range of motion in the knee.

Possible Complications of a Total Knee Replacement

As with all major surgical procedures, complications can occur. The most common complications following knee replacement are:

  • Thrombophlebitis
  • Infection in the joint
  • Stiffness of the joint
  • Loosening of the joint

This is not intended to be a complete list of the possible complications, but these are the most common.


Thrombophlebitis, sometimes called Deep Venous Thrombosis (DVT), can occur after any operation. It is more likely to occur following surgery on the hip, pelvis, or knee. DVT occurs when the blood in the large veins of the leg form as clots within the veins. This may cause the leg to swell and become warm to the touch and painful. If the blood clots in the veins break apart they can travel into the lung. Once in the lung they can get lodged in the capillaries of the lung and cut off the blood supply to a portion of the lung. This is called a pulmonary embolism. Pulmonary means “lung”. An embolism is a fragment of something traveling through the vascular system. Most surgeons take preventing DVT very seriously. There are many ways to reduce the risk of DVT, but probably the most effective is getting the patient moving around as soon as possible!

Some of the commonly used preventative measures include:

  • Pressure stockings to keep the blood in the legs moving.
  • Medications that thin the blood and prevent blood clots from forming.


Infection can be a very serious complication following an artificial joint replacement. The chances of getting an infection following a total hip replacement are probably around 1 in 100. Some infections may show up very early – before the patient leaves the hospital. Others may not show up for months or even years after the operation.


In some cases, the ability to bend the knee does not return to normal after an artificial knee replacement. Many orthopedic surgeons are now using a machine known as a CPM machine (Constant Passive Motion) immediately after surgery to try and increase the range of motion following an artificial knee replacement. Other orthopedic surgeons rely on physical therapy beginning immediately after the surgery to regain the motion. It is not clear which is the best approach. Both approaches have benefits and risks, and the choice is made by the surgeon based on his experience and preferences.

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 an increase in scarring after surgery can lead to an increasingly stiff knee. If this occurs, we may recommend taking the patient back to the operating room, placing them under anesthesia once again, and forcefully manipulating the knee to regain motion. Basically, this allows us to break up and stretch the scar tissue without the patient feeling it. The goal is to increase the motion in the knee without injuring the joint.


The major reason that artificial joints eventually fail continues to be loosening of the joint where the metal or cement meets the bone. There have been great advances in extending the life of an artificial joint, yet most joints will eventually loosen and require a revision. Hopefully, one can expect 15-20 years of service from an artificial knee. In some cases, the knee will loosen earlier than that. Just like a diseased knee, a loose joint causes pain. Once the pain becomes unbearable, another operation will probably be required to replace the knee. As seen a total knee replacement again is a very technically demanding operation. Just like the hip, if it is not done properly then the life span of the artificial joint is less, it may dislocate from its position and may still be painful.

Knee Replacement Frequently Asked Questions
  • How long should I use the pain medication?

    This is different for each patient. Some patients are able to use Tylenol or Advil after they leave the hospital and others require narcotic pain medication. Generally, you should try to decrease the use of medications as time passes.

  • When should I go to outpatient therapy?

    If you are going home or to a rehab center, in either case you should schedule physical therapy within a few days of your release. If you do not have a prescription for physical therapy, please call our office and we will provide a prescription and list of physical therapists in your area.

  • When can I go to the dentist?

    Not for three months after surgery. As the knee is gently healing and there is increased blood flow to this area, there is a higher risk of infection.

    You must take prophylactic antibiotics for the next two years, if if any of the following pertain to you:

    1. You have had another surgical procedure
    2. You have had any dental procedure
    3. Any lung, bladder, or colonoscopy procedure
    4. You develop any kind of infection.

    Immuno compromised patients with Rheumatoid Arthritis, Lupus, Insulin Dependent Diabetes, chemical or radiation induced immuno-supression, will need to take prophylactic antibiotics for life.

    Total knee replacement patients who require dental work on gums or roots must adhere to the following antibiotic procedure:

    For patients not allergic to Penicillin: Cephalexin, Cephradine or Amoxicilin: 2 grams orally 1 hour prior to the dental procedure.

    For patients allergic to Penicillin: Clindamycin: 600mg orally 1 hour prior to the dental procedure.

    Patients should adhere to this regimen for the first two years following joint replacement. Immunocompromised patients, including those with inflammatory arthropathies, rheumatoid arthritis, drug or radiation-induced immunosuppression, insulin-dependent diabetes or any other major medical problem should follow this antibiotic routine indefinitely.

    Antibiotics can reduce the risk of infection but cannot completely eliminate that risk. Preventing infection must be the concern of all the healthcare professionals who treat you. MAKE SURE YOU INFORM YOUR PHYSICIAN AND DENTIST THAT YOU HAVE HAD A TOTAL KNEE REPLACEMENT.

  • When can I drive?

    You should not drive as long as you are taking narcotic pain medications. If it is your left knee, you can resume driving when you feel a bit more normal (usually in about three weeks, as long as vehicle is an automatic). If it is your right knee, I would like to evaluate you at 6 weeks-hence no driving before 6 weeks.

  • Why does my knee click after surgery?

    Clicking after surgery is normal. The clicking is a result of the metal and the plastic parts of your knee replacement coming in contact during motion. Over time, you will become accustomed to it.

  • Is a lot of swelling normal?

    Fluid can accumulate in the legs due to the effects of gravity. Usually it is not a problem in the hospital, but it may get worse when you go home or to a rehab center, because you will be moving around more, To reduce swelling, you should elevate your legs at night. Lie on your back and place pillows underneath your legs so that they are above the heart. Do not place a pillow under your knee at night as it prevents the knee from becoming straight. However if your ankle and leg swelling does not get better after keeping your leg elevated at night call, please call your surgeon. To reduce swelling in the knee, use an ice pack. Apply for 20 minutes, three times per day.

  • How long do I have to wear the stockings?

    You should wear the stockings on both legs. Have someone help you with them in the morning, wear then throughout the day and then take them off at night. If you did not get the stockings from the hospital you can purchase knee height, medium, compression, surgical stockings from any pharmacy. Try to wear them for 6 weeks if possible. This helps to reduce leg swelling and prevent blood clot formation in your leg.

  • Can I travel?

    In general, I would like to see you before you travel by air. If you are traveling by car you should be sure to take frequent breaks so that you do not feel stiff in getting up. On an airplane, I would like you to wear compression stocking and take a couple of walks during the flight. Request aisle and/or bulk head seats so you will have more space.

Orthopaedic Specialists of Connecticut, also known as Orthopedic Specialists of Connecticut, based in Brookfield, CT and Danbury, CT, provides comprehensive orthopaedic care, sports medicine, joint replacements, and interventional pain management to patients of all ages.

Orthopaedic Specialists of Connecticut, also known as Orthopedic Specialists of Connecticut, provides orthopedic care including: orthopedic examination, foot surgery, ankle surgery, hand surgery, hip surgery, hip replacement, hip resurfacing, knee surgery, knee replacement, orthopedic oncology, shoulder surgery, elbow surgery, and MAKOplasty.

Orthopaedic Specialists of Connecticut, also known as Orthopedic Specialists of Connecticut, also provides sports medicine, physical therapy, pain management, interventional pain management, radiology, x-ray, ultrasound, cortisone injection, and PRP injections.

Orthopaedic Specialists of Connecticut, also known as Orthopedic Specialists of Connecticut, treats sprains, fractures, ligament tears, arthritis, musculoskeletal pain, neurological pain, cancer pain, neck pain, and back pain.