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Bahri Orthopaedics

Partial and Total Knee Replacement

Knee Replacement Figure 1
Figure 1

Partial and Total Knee Replacement

Simple tasks such as walking and standing may become difficult if you have advanced arthritis of the knee. If the problem is severe enough, you may have pain with sitting or at rest. If medications, activity modification, and walking aides are no longer beneficial, knee replacement surgery may be an option for you. By replacing the arthritic surfaces of the knee, we can relieve pain, correct leg deformity, and promote a return to normal activities.  Knee replacement surgery is one the most commonly performed orthopedic procedures in the U.S. with approximately 600,000 knee replacements performed annually.

 

Anatomy

Knee Replacement Figure 2
Figure 2

The knee is made up of the femur (thigh bone), tibia (shin bone), and the patella (kneecap). Ligaments attach to the femur and tibia to provide stability. The quadriceps and hamstring muscles give the knee strength. The joint surfaces of the knee are covered with cartilage, a smooth substance that cushions the bones and reduces friction to allow for easy movement (Figure 1).  The remaining surfaces of the knee are covered by a separate tissue liner called synovial tissue. This tissue produces fluid that lubricates the knee.  Arthritis is a disease process that involves disruption of the structures of the knee resulting in pain, motion loss, and loss of function (Figure 2).

Common causes of arthritis

Osteoarthritis, rheumatoid arthritis, and traumatic arthritis are the most common forms of arthritis.  Osteoarthritis usually occurs in people over the age of 50 years. There is often a positive family history of arthritis. The cartilage within the knee joint deteriorates resulting in "bone on bone", causing knee pain and stiffness. Rheumatoid arthritis is an auto-immune disease in which the synovial membrane becomes inflamed resulting in auto-destruction  of the cartilage. This eventually causes cartilage loss, pain, and stiffness. Traumatic arthritis may occur after a significant knee injury such as a dislocation, and/or fracture. This form of arthritis typically occurs over a shorter period of time, and may result in surgical intervention at an earlier age than what is seen with osteoarthritis.

When is knee replacement surgery right for you?

There are several scenarios that may indicate the need for knee replacement surgery:

  1. Severe knee pain and stiffness that prevents your ability to perform simple daily activities such as standing and walking short distances.
  2. Knee pain at rest or at night
  3. Chronic knee pain that does not improve with rest or anti-inflammatory medications
  4. Knee deformity ("bow-legged or knock-kneed")
  5. Lack of relief from pain medications
  6. Lack of improvement with cortisone injections, physical therapy, or other surgeries

The majority of patients who undergo total knee replacement are aged 60 to 80. Treatment, though, is individualized based upon the patient's pain and disability, not chronologic age.

What to expect during your orthopedic evaluation

Your primary care physician will usually refer you to an orthopedic surgeon for discussion of treatment options regarding arthritis of the knee. The orthopedic evaluation usually consists of a medical history, physical examination, x-rays, and referral for additional lab tests or imaging studies (i.e. MRI). After completion of these studies, your orthopedic surgeon will review the results with you and discuss whether knee replacement surgery is the most appropriate option to relieve your pain and improve your function. Your surgeon will likely discuss other treatment options if you are not a candidate for intervention. Your orthopedic surgeon review the potential risks and complications of knee replacement surgery, including those related to the surgery and those that can occur after your surgery.

Getting ready for surgery

Once it has been determined that you need surgery, there are a series of necessary steps that need to be completed prior to intervention.

You will be asked to complete a physical examination by your family physician several weeks before surgery to gauge your health and to identify any issues that could interfere with your surgery. Some tests may be needed, such as blood  and electrolyte levels. Urine samples may be tested and an electrocardiogram may be obtained.  Your knee and leg should not have any skin infections or irritation.  Your orthopedic surgeon  should be aware of all 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 infection after knee replacement is rare, an infection can occur if bacteria enter your bloodstream. Treatment of  dental diseases (such as tooth removal and gum work) should be considered before your total knee replacement surgery.

Evaluation by a urologic surgeon  should be undertaken for individuals with a history of recent or frequent urinary infections.

Knee Replacement Figure 3
Figure 3

Surgery

You will be admitted to the hospital on the day of your surgery. The most common types of anesthesia are general anesthesia, in which you are asleep throughout the procedure, and spinal or epidural anesthesia, in which you are awake but your legs are "asleep". The anesthesia team  in conjunction with you and your surgeon will determine which type of anesthesia will be ideal. The surgery takes approximately 2 hours. Your orthopedic surgeon removes the diseased cartilage and bone, and places new metal and plastic  (polyethylene) joint materials to correct the alignment of the knee and restore function of your knee (Figure 3).

There are several types of implant designs and materials which are currently used in total knee replacement surgery, nearly all of which consist of three components: the femoral component (made of a highly polished strong metal), the tibial component (made of a durable plastic often held in a metal tray), and the patellar component (plastic). Currently there are newer techniques that allow for customized implants to be placed or allow for customized instruments to be used during the surgical procedure.  Custom implants are specifically designed for each individual, allowing for preservation of the person's bone if future procedures are necessary. Customized instruments allow for improved efficiency during the operation which reduced surgery time and blood loss. Additional imaging studies (CT scan, MRI) may be necessary to take advantage of these techniques. Your surgeons at Bahri Orthopedics and Sports Medicine have the additional training and expertise in the use of these new methods of knee replacement surgery.

After Surgery

You will be admitted to the hospital for several days after surgery. You will have some discomfort, but medication will be provided to you to make you as comfortable as possible.  Pain management is usually coordinated effort between your anesthesiologist and surgeon. Sometimes nerve blocks are used to provided temporary pain relief after surgery. Walking and knee movement are encouraged after surgery. Your surgeon may use a knee appliance that slowly bends and extends your knee while you are in bed. The continuous passive motion (CPM) exercise machine, decreases leg swelling by elevating your leg and improves your venous circulation by moving the muscles of your leg. Your surgeon will prescribe one or more measures to help prevent blood clots such as support hose,  compression sleeves or boots, and blood thinners such as enoxaparin, warfarin or aspirin. Physical therapy is initiated on the day after surgery to strengthen the leg and restore knee motion with the goal being independent ambulation.  Case management is usually involved to assist you in placement into an inpatient rehabilitation facility versus home health care. 

After Discharge

Your staples or sutures are removed approximately two weeks after surgery.  Your incisional wound should not be submerged in water until it has healed The wound may be bandaged daily to prevent irritation from clothing or support stockings.  It is extremely important to continue your exercise regimen at home after discharge.  You should be able to resume most 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. Driving is usually allowed by your surgeon at approximately 6 to 8 weeks after surgery. This allows time for you sit comfortably in your car and re-establish reaction time for braking and acceleration.

Expectations after knee replacement surgery

The vast majority of individuals who undergo total knee replacement surgery experience significant reduction in knee pain and  improvement in the ability to perform activities of daily living; however,  knee replacement surgery will not allow you to do more than you could before you developed arthritis. You will be instructed to avoid some types of activity such as jogging jumping sports,  and high impact aerobics for the rest of your life. Current ten-year survival rates for fixed and mobile bearing knee replacements range from 90% - 95%. The success of your surgery will depend on how well you follow your orthopedic surgeon's instructions.  Improvement of knee motion is one of the primary goals of knee replacement surgery, but restoration of full motion is uncommon. Kneeling may be uncomfortable, but it is not harmful to the implant. Your new knee will likely trigger metal detectors required for security in airports and some buildings. To maintain the function of the knee, we recommend that you participate in a regular light exercise program. Your dentist or oral surgeon should be made aware of your artificial knee. You should be given antibiotics before all dental surgery for the duration of your life. You should see your orthopedic surgeon periodically for routine follow-up once a year.