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Knee Replacement Surgery

What is a knee replacement?

We should distinguish between a total knee replacement and a unicompartmental knee replacement. The total knee replacement replaces the full bottom and top of the joint, whereas the unicompartmental replacement only replaces one side of the knee, top and bottom.

Both have good clinical results and a long track record. Traditional total knee replacement involves a bigger incision and is more invasive than a partial knee replacement. However, a minority of patients are suitable candidates for the partial replacement. The majority of patients have significant wear and tear on both sides of the knee.

In both knee replacements the part that replaces the upper leg is made from a metal component and the part that replaces the lower leg has a metal base with a plastic liner. Note that it is actually more a resurfacing rather than a replacement since only the surfaces are replaced. There are differences in the types of the individual replacements and these have slightly different characteristics. It is the decision of your consultant to determine which knee is most suitable for you.

What should I expect from my knee replacement?

Initially it should be expected that there is some pain from the surgery, however this pain should decrease day by day. Your knee may feel a bit stiff in both flexion (bending) and extension (straightening), and may be swollen for a few weeks but with exercise this will result in a knee that functions much better than previously.

Before Coming in to Hospital

  • Start making arrangements for going home after surgery.
  • Decide who will take you home from hospital
  • If you live alone or are at home alone during the day, plan for family or friends to help you around the house for the first week or two. You will need help with laundry, TED’s, cleaning and shopping after you get home
  • Start getting your home ready. Look around your house and see if there is anything that may be a problem for someone using a stick/crutches following surgery
  • Take up all scatter rugs and tape down edges of large area rugs
  • Keep walkways clear of furniture and electrical/telephone cord
  • It may be a good idea to obtain a high chair with arms to make it easier to sit/stand
  • You may wish to raise your bed as well
  • Place emergency numbers near or in the telephone. Make sure a telephone is near your favourite chair and close to the bed
  • Stock up on groceries and pre-cooked meals so they only have to be reheated and served. Place a night light in a dark hallway and possibly have a flashlight at hand for a nightly visit to the bathroom
  • Place items you use every day at arm level to avoid reaching up or bending down
  • If possible, get yourself fit before the operation. Choose exercises like swimming or cycling if your knee can tolerate them.

What Happens When I Come into Hospital?

  • You will normally be admitted on the day of surgery. This will give you time to settle in and allows staff to introduce themselves and any necessary tests to be done
  • When you arrive at the admissions office on the ground floor, your details will be taken and you will be shown to your room
  • A nurse will admit you and the physiotherapist will see you to discuss the operation and the exercises you must do after surgery
  • The anaesthetist will visit you before your operation and explain to you about the anaesthetic
  • It is important that you understand what operation you are having and what is written on the consent form before you sign it. If you are unsure about anything, please ask any member of the healthcare team
  • You will not be allowed to eat or drink anything for six hours before your operation to prevent anaesthetic complications. Your nurse will tell you when you have to stop eating and drinking. It could be from midnight or from 6am, depending on the time of your operation. Ensure you know this in case anyone offers you anything.

What Happens When My Operation is Finished?

  • Following your operation you will be looked after by a nurse in the recovery area near the theatres for an hour or two
  • The nurse will measure your blood pressure and pulse while your anaesthetic wears off. As a routine check the nurse will also measure the pulse in your feet
  • When you wake up you will be given some pain medication. If you need anything, or are in pain, please tell the nurse
  • When you are comfortable and the theatre staff feels you are ready, you will be taken back to the ward
  • You will have a bandage around your knee and a drain. The drains allow for excess blood to escape and will be removed 24 to 48 hours post surgery, depending on the instructions of your consultant
  • Most consultants wish for their patients to use the Flowtron system. This is a DVT (deep vein thrombosis) preventative measure, where cuffs around the lower legs inflate and deflate with air, increasing the circulation, thus reducing the risk of a blood clot/DVT.

What Happens When I am Back on the Ward?

  • You should commence your breathing and circulation exercises immediately (as featured on the following page) to help prevent any risk of developing a chest infection or blood clot/DVT
  • On the first morning after surgery, you will be seen by your physiotherapist who will assess you and start your postoperative rehabilitation and mobilisation
  • On the first day you will also start with the exercise to activate your quadriceps (thigh muscle) and you will also be encouraged to fully straighten your knee
  • You will have a routine x-ray of the knee and maybe a blood test.

Bed exercises - Breathing and circulation exercises to be done hourly

1. Deep Breathing Exercises

Take a deep breath in though your nose trying to expand your lower ribs and then breath out completely through your mouth. Repeat 3 times. If this brings up phlegm, cough to clear.

2. Ankle Pumps

Flex your feet towards your face and then point them away. Draw circles with your feet. Do this for a few minutes.

3. Gluteal (buttock) Contractions

Clench your buttocks together and hold for a few seconds. Repeat 5 to 10 times.

Home exercise programme

It is important to first rest your leg fully extended. This can be done by rolling up a towel and resting your heel on this. Do this for periods of 15-20 minutes at least. This will create a straighter knee and better performance of the next 3 exercises.

Whilst doing your exercises expect some discomfort around the knee, this is normal. However, don’t force any movements or push through pain.

Do the next exercises 4 to 5 times a day. Start with 5 repetitions initially and build up to 10 reps.

Remember that using an ice pack may prove extremely helpful, both to reduce the swelling and temperature, but it will also have a pain reducing effect. The best time to use ice is after your exercises, leave the ice pack on for 15-20 minutes only.

1. Static Quads Contractions

With your leg straight out in front of you place a rolled up towel under your heel. Pull your foot towards you, tighten your thigh muscles and press your knee down into the bed. Hold for 5 seconds and then relax. Repeat 10 times.

2. Inner Range Quads

Place a rolled up towel under the knee so that your knee is slightly bent. Now pull your foot up towards you and straighten the knee. Keep your knee on the roll. Hold for 5 seconds and then relax. Repeat 10 times.

3. Straight Leg Raises

First bend your opposite (good) leg and ensure that you are not sitting too upright. Tighten the thigh muscles of the operated leg and pull your toes up towards you, then raise the whole leg as straight as possible a few inches off the bed. Hold for 5 seconds and lower. Repeat 10 times.

4. Active Knee Flexion

Start with leg straight on bed. Then slowly slide your heel up the bed so that your hip and knee bend. Bend until you feel it tighten. This is often restricted due to swelling.

5. Sitting

  • First bend your knee as far as possible, sliding your heel along the floor. You may push with your unoperated leg. Pause. Repeat 10 times.
  • Set your abdominal muscles, move your toes up towards you, now raise your leg. Hold for 5 seconds. Repeat 10 times.
  • Then fully straighten. Repeat 5-10 times


Before you get up from the bed the physiotherapist will first assess the activity of the quads or thigh muscles. Expect to start on a zimmer frame or walking frame. After a few days this will be replaced by crutches. Soon you will use one crutch only and if your leg is good enough you may leave the hospital with only a stick.

Standing exercises

It is advised that you do the following exercises whilst holding on to the exercise rail or, when at home, to the back of a heavy chair. Again like with the bed exercises do them 4 to 5 times a day, starting with 5 repetitions building up to 10 reps.

1. Mini Squats

From a standing position bend both knees about 30 degrees as if you are sitting down on a chair. Hold for a second and slowly fully straighten again. Repeat 5-10 times.

2. Hamstring Curl

Bend your operated leg up behind you as far as possible. When straightening try to fully straighten before you bring your foot to the floor. Repeat 5-10 times.

3. Heel Raises

Without putting too much weight through your hands, raise your heels as high as possible. Hold for one to two seconds, relax and repeat. Repeat 5-10 times.

4. Knee Extensions in Standing

Stand up straight, brace both knees back to straighten them by tightening your thighs and buttocks. Hold for 5 seconds and then relax. Repeat 10 times.

Going up and down stairs

Going up the stairs

Hold the rail on one side and your stick or crutch on the other side. Place the unoperated leg up first followed by the stick and the operated leg to the same step. Remember the “Golden Rule”: GOOD (unoperated) leg UP to heaven, BAD (operated) leg DOWN to hell.

Going Down the Stairs

Hold the rail on one side and your stick or crutch on the other side. Place the stick or crutch and the operated leg down first, followed by the unoperated leg onto the same step. Remember the stick and the operated leg move together.

Going up and down stairs with 2 elbow crutches

Going up stairs

Place unoperated leg up first, then crutch and operated leg together.

Going down stairs

Place crutches with operated leg down first, then unoperated leg.

When do I go home?

Being ready for discharge is dependent on several different things. Most important is that the wound is satisfactory, that you are comfortable and any pain is controlled. You should also be able to manage safely at home. Sometimes a convalescent home may be a good interim solution for those who need some extra time before going home. You should expect to leave the hospital using one crutch, be able to climb stairs and to walk a short distance. It is recommended that you continue your physiotherapy after discharge, to optimise the function of your knee.

General advice

  • A rail installed by the bath/shower wall should provide you with some extra stability when getting in and out of the bath
  • Non-slip mats in, and possibly outside, the bath/shower would be sensible
  • A pillow between your knees at night when lying on your side should make you more comfortable
  • In some cases where the “good leg” is not that strong, a raised toilet seat will make sitting/standing from the toilet easier
  • Once at home try to gradually increase your level of activity, walking a little further each day. You should still use your walking aid as advised
  • Tell your GP that you have had a knee joint replacement and inform him/her if you are unwell or develop an infection, skin rash, etc (especially if this is in the same leg). If you need dental treatment, tell your dentist that you have had a joint replacement. The same applies if you have had any other form of surgery or treatment. Antibiotics should be used with such procedures to cover you against the risk of infection.

Possible Complications

As with all surgeries there is a risk of complications, however small they may be. It is important that you are aware of them.

Early Complications

One of these is the risk of infection, and although the risk is small the consequences can be significant. That is why your consultant and the medical team will do everything they can to minimise the risk of infection.
Although very unlikely, it is possible that a blood clot (or DVT) develops in one of the deeper veins in the leg. To lower the risk we will mobilise you as soon as possible following surgery and ask you to do your bed exercises regularly. Some consultants also use an air pump system called Flowtron.

Late Complications

Sometimes a prosthesis loosens, but when this happens this is usually after years of use. It is a complication that can be caused by the dynamics of the bone and the cement bonding in the long term.

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