Total Knee Replacement

What is a total knee replacement?
A knee replacement involves removing a thin layer of bone from the damaged surface of the femur (thigh bone), using special instruments which remove the correct thickness of bone.  The removed bone is then replaced by a thin layer of metal, approximately the same dimensions and thickness as the bone which was removed.

In a similar fashion the upper end of the tibia (shin bone) is removed and is replaced with a metal plate.  In between the metal place on the femur and the metal place on the tibia is a thin wafer of plastic which acts as the new cartilage.  The back part of the kneecap (patella) is also resurfaced with a thin layer of plastic to get rid of the arthritis in this area. 

After the knee has been replaced, the metal covering the end of the femur rubs against the plastic covering the metal on the end of the tibia, preventing bone from rubbing on bone and giving relief of pain.  The plastic is a high density polyethylene material which has a very low wear-rate and very low frictional resistance when rubbing against a highly polished metal surface. 

What are some of the possible complications of surgery?
While complications are not common, all surgery has associated risks.  Possible complications include stiffness of the knee after surgery or continued pain.  Other complications include infection, bleeding, nerve injury, blood clots, or problems with anesthesia or underlying medical conditions.  In the hospital, we usually have a medical doctor follow patients for their medical conditions and we take every precaution against blood clots and infection. 

What kind of anesthesia is used?
Total knee replacement is usually performed with general anesthesia (going to sleep), but sometimes it may be performed with regional anesthesia (spinal or epidural block).  The type of anesthesia will depend on your choice, as well as what the anesthesiologist best recommends for you.  I recommend that you undergo a continuous femoral nerve block, which is performed by anesthesia before your surgery.  This is an excellent tool to minimize pain in a patient’s knee for the first 2-3 days.  The difference has been amazing, in that a lot of patients are not using much oral medication for the first several days and are much more relaxed and are improved during physical therapy.

What do I need to do to prepare for surgery?
My staff will help to set up the surgery through your insurance company and will instruct you on any paperwork that may be necessary.  If you are over the age of 50, or have significant health conditions, you may require an EKG and a chest x-ray.  You may also need to see your internist or family doctor to obtain a letter of medical clearance. 

The day before surgery a member of the hospital will contact you about what time to arrive for your surgery.  You may not eat or drink anything after midnight before the surgery. 

How long will I be in the hospital?
Hospitalization is usually a 3 to 4 day length.  Sometimes patients get out sooner, but rarely do patients spend any time longer than 4 days.  Sometimes patients are not able to go home but are required to go to a rehab or skilled nursing facility to get added physical therapy before they go home.  This will be individualized while you are in the hospital and social services will help us coordinate this if it is a necessary option. 

What happens the day of surgery?
The day before surgery you will be told what time to report to the hospital.  You will be admitted and taken to a pre-operative holding area where you are prepared for surgery.  You will be asked several times which extremity I am operating on.  Please note that you are asked this question many times on purpose.   

Please be aware that the process of getting checked in, prepared for surgery, undergoing the operation, and recovering from anesthesia takes the majority of the day.  I would recommend that you and your family members bring along some reading material to make the process easier for all.   

After your surgery, you will then be taken to the recovery room to be monitored.  Once the effects of anesthesia have worn off and your pain is under good control, you will be transferred to your room in the hospital.  All of the rooms at Des Peres Hospital are private rooms. 

After your surgery you will have a drain in your joint as well as a Foley catheter in your bladder.  The drains are usually removed the next day in all patients and the Foley catheter is removed the next day for men.  In women, I usually leave the Foley catheter in for several days until a patient is able to get up better and get to the bathroom much easier.

How should I care for my knee after surgery?
During your hospitalization you will begin physical therapy the day after your surgery as well as a continuous passive motion (CPM) machine.  During the hospitalization you will be helped with walking, you will be instructed on stair climbing and range of motion exercises.  For the first day or two your knee might be in an immobilizer because of the use of the femoral nerve block.  The femoral nerve block helps out with post-operative pain but may make your muscles weak for a day or two.  To ensure that your knee does not give out, we may use a knee immobilizer while doing some of the physical therapy exercises while walking.  You certainly do not need to have that on in bed or obviously when you are on the continuous passive motion machine. 

After you are discharged from the hospital, you will have a continuous passive motion machine at home and will have a home physical therapist usually coming for three times a week for two to three weeks. 

You will be given a prescription for pain medication and an antibiotic.  You will be instructed to take a regular aspirin daily to minimize the effects of blood clots. 

You may shower when you get home from the hospital.  If you have a safe shower, you may go ahead and take your dressing off and enter the shower.  I do not want you soaking the knee, but do not mind a little shower water coming down across your knee.  After you get out of the shower you will be instructed to take a little bit of hydrogen peroxide on a clean washcloth and dab off the knee to clean it.  You will then place a dressing on for that day.  If you do not take a shower, we still want you to clean the incision off once a day with hydrogen peroxide. 

You will be instructed on how to use an ambulatory device after your surgery while in the hospital. Most patients elect to use a walker and this will be supplied to you.  You may put as much weight as you feel comfortable on your knee, but you certainly will advance your weight-bearing with the walker until you are able to switch to a cane.  The time that people take to switch to a cane varies, but some people can do that after a week and are comfortable doing so. 

Your regular diet will be resumed in the hospital as tolerated. 

Follow up:
A follow up appointment will be made at two weeks post-operatively, where we will remove the staples. 

What will rehabilitation involve?
The rehabilitation is based on several goals:  1) allowing the tissues to heal; 2) regaining motion; 3) regaining strength; and 4) return to normal activities or activities that you have not been able to do for some time because of your arthritis.  Most of the time patients will not need any formal physical therapy after the home physical therapy.  However, if a patient is having trouble with motion, an outpatient physical therapy program may be recommended.  A continuance of the exercises learned in the hospital and by the home physical therapy after discharge from the hospital can usually be performed by a patient to continue to obtain better range of motion and better strength.

When can I return to regular activities or work?
A return to a desired activity level certainly depends on how fast a patient may heal.  In general, people may return to a sedentary type job at four weeks or so.  Certainly more strenuous jobs will take longer and may be in the neighborhood of two to three months.   

I want you to have good motion, strength, and control of your knee before returning to your job.  How quickly you return depends on several factors including:  1) your rate of healing; 2) the presence of any complications; 3) how well you follow physical therapy and post-operative instructions; and 4) how hard you work in rehabilitation.