Sports Medicine

Uni-Condylar Knee Replacement


Uni-Condylar Knee Replacement is a procedure where only a part of the knee joint is replaced through a smaller incision than would normally be used for a total knee replacement.

Uni-Condylar knee replacements have been performed since the early 1970′s with mixed success. Over the last 25 years, implant design, instrumentation, and surgical technique have improved markedly, making it a very successful procedure for unicompartmental arthritis. Recent advances allow us to perform the procedure through a smaller incision and, therefore, the procedure is not as traumatic to the knee, making recovery quicker.

Total Knee Replacement surgery replaces the ends of the femur (thigh bone) and tibia (shin bone) with plastic inserted between them and usually the patella (knee cap).


Arthritis is a general term covering numerous conditions where the joint surface (articular cartilage) wears out. The joint surface is covered by a smooth articular surface that allows pain free movement in the joint.

Osteoarthritis is a condition where the articular cartilage wears out, causing the bone ends to rub on one another and cause pain and inflammation. There are numerous conditions that can cause arthritis and often the exact cause is never known. In general, the condition affects people as they get older.

Other Causes Include:

  • Trauma (fracture)
  • Increased stress e.g., overuse, overweight, etc.
  • Infection
  • Connective tissue disorders
  • Inactive lifestyle- e.g., Obesity, as additional weight puts extra force through your joints which can lead to arthritis over a period of time
  • Inflammation e.g., Rheumatoid arthritis

In an Arthritic Knee

  • The cartilage lining is thinner than normal or completely absent. The degree of cartilage damage and inflammation varies with the type and stage of arthritis.
  • The capsule of the arthritic knee is swollen.
  • The joint space is narrowed and irregular in outline; this can be seen in an X-ray image.
  • Bone spurs or excessive bone can also build up around the edges of the joint.

The combinations of these factors make the arthritic knee stiff and limit activities due to pain or fatigue.


  • The diagnosis of osteoarthritis is made on history, physical examination, and X-rays.
  • There is no blood test to diagnose osteoarthritis (wear & tear arthritis).

Advantages & Disadvantages

The decision to proceed with Knee Replacement Surgery is a cooperative one between you, your surgeon, your family, and your primary care doctor.

The benefits following surgery are relief of the symptoms of arthritis. These include:

  • Severe pain that limits your everyday activities including walking, shopping, visiting friends, getting in and out of chairs, gardening, etc.
  • Pain waking you at night
  • Deformity- either bowleg or knock knees
  • Stiffness

Prior to surgery, you will usually have tried some conservative treatments such as simple analgesics, weight loss, anti-inflammatory medications, modification of your activities, cortisone injections, or viscosupplementation.

Advantages of Uni-Condylar Knee Replacement

  • Smaller operation
  • Smaller incision
  • Not as much bone removed
  • Shorter hospital stay
  • Shorter recovery period
  • Blood transfusion rarely required
  • Better movement in the knee
  • Feels more like a normal knee
  • Less need for physiotherapy
  • Able to be more active than after a total knee replacement
  • The big advantage is that if, for some reason, the procedure is not successful or fails many years down the line, it can be revised to a total knee replacement without difficulty.

      Disadvantages of Uni-Condylar Knee Replacement

      • Not quite as reliable as a total knee replacement in taking away all pain
      • Long-term results not quite as good as total knee replacement

        Who is suitable and who is not?

        • Ideally, patients should be over 50 years of age
        • Patients with pain and restricted mobility that interferes with their lifestyle
        • Patients with clinically significant arthritis in one knee compartment confirmed on X-ray

        Who is not suitable?

        • Patients with arthritis affecting more than one compartment
        • Patients with severe angular deformity
        • Patients with inflammatory arthritis e.g.. rheumatoid arthritis
        • Patients with an unstable knee
        • Patients who have had a previous osteotomy
        • Patients who are involved in heavy work or contact sports


        • Your surgeon will send you for routine blood tests and any other investigations required prior to your surgery.
        • You will be asked to undertake a general medical check-up with your primary care doctor.
        • You should have any other medical, surgical or dental problems attended to prior to your surgery.
        • You should make arrangements with your family and friends for help around the house after surgery.
        • Cease aspirin and anti-inflammatory medications 7 days prior to surgery as they can cause bleeding.
        • Cease any naturopathic or herbal medications 10 days before surgery.
        • Stop smoking as long as possible prior to surgery.

        Day of Surgery

        • You will be admitted to the hospital usually on the day of your surgery.
        • Further tests may be required on admission.
        • You will meet the nurses and answer some questions for the hospital records.
        • You will meet your Anesthetist who will ask you a few questions.
        • You will be given hospital clothes to change into and have a shower prior to surgery.
        • The operation site will be shaved and cleaned.
        • Approximately 30 minutes prior to surgery, you will be transferred to the operating room.

        Surgical Procedure

        Each knee is individual and knee replacements take this into account by having different sizes for your knee. If there is more than the usual amount of bone loss sometimes extra pieces of metal or bone are added.

        Surgery is performed under sterile conditions in the operating room under spinal or general anesthesia. You will be on your back and a tourniquet applied to your upper thigh to reduce blood loss. Surgery will take approximately two hours.

        The patient is positioned on the operating table and the leg prepped and draped.

        A tourniquet is applied to the upper thigh and the leg is prepared for the surgery with a sterilizing solution.

        An incision around 7cm is made to expose the knee joint.

        The bone ends of the femur and tibia are prepared using a saw or a burr.

        Trial components are then inserted to make sure they fit properly.

        The real components (Femoral & Tibial) are then put into place with or without cement.

        The knee is then carefully closed with sutures and staples, a drain is usually inserted, and the knee is then dressed and bandaged.

        Post-operation Course

        When you wake, you will be in the recovery room with intravenous drips in your arm and a number of other monitors to check your vital observations. You will be given pain medications as needed to help with pain control. To avoid lung congestion, it is important to breathe deeply and cough up any phlegm you may have.

        Once stable, you will be taken to the ward. The post-op protocol is surgeon-dependent but, in general, your drain will come out at 24 hours. You will be allowed to bear weight on your knee right away and you may get out of bed, sit in a chair, and walk around your room as tolerated. The surgical dressing will be changed on the second post-op day to make movement easier. Your rehabilitation and mobilization will be supervised by a physical therapist. Your medications and overall health will be managed by a hospitalist.

        Your surgeon will use one or more measures to prevent blood clots in your legs. These include aspirin, blood-thinning medications, inflatable leg coverings, and compression stockings.

        Usually, you will remain in the hospital for 2-3 days and then, depending on your needs, you can either return home or proceed to a rehabilitation facility. You will be discharged from the hospital being able to bear weight on your knee as tolerated. You may use a walker or cane if needed.

        When you go home, you need to take special precautions around the house to make sure it is safe. You may need rails in your bathroom or to modify your sleeping arrangements, especially if they are up a lot of stairs.

        You will receive home physical therapy for your knee for two weeks following surgery. Many of the long-term results of knee replacement surgery depend on how much work you put into your rehabilitation following your surgery. Patients who work hard in physical therapy following surgery tend to get better faster.

        You will follow up with your surgeon two weeks after surgery. The surgical staples used to close the knee incision are removed at this visit. You will then be referred for outpatient physical therapy.

        Bending your knee is variable, but by 2 weeks it should bend to at least 90 degrees. The goal is to obtain 120-130 degrees of movement and be able to fully straighten your knee.

        Once the surgical incision is healed, you may shower. You can drive at about 6 weeks once you have regained control of your leg. You should also be walking reasonably comfortably by 6 weeks. More physical activities, such as exercise and leisure sports, usually take 3 months to do comfortably.

        You will usually have a 6-week check-up and a 12-week check-up with your surgeon who will assess your progress. You should continue to see your surgeon for the rest of your life to check your knee and take X-rays. This is important as sometimes your knee can feel excellent but there can be a problem only recognized on X-ray.

        You are always at risk of infections, especially with any dental work or other surgical procedures where germs (bacteria) can get into the blood stream and find their way to your knee.

        If you ever have any unexplained pain, swelling, redness, or if you feel generally poor, you should see your doctor as soon as possible.

        Risks and Complications

          As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.

          It is important that you are informed of these risks before the surgery takes place.

          Complications can be medical (general) or local complications specific to the knee.

        Medical Complications

        Medical complications include those of the anesthetic and your general well-being. Almost any medical condition can occur so this list is not complete. Complications include:

        • Allergic reactions to medications
        • Blood loss requiring transfusion with its low risk of disease transmission
        • Heart attacks, strokes, kidney failure, pneumonia, bladder infections
        • Complications from nerve blocks such as infection or nerve damage
        • Serious medical problems that can lead to ongoing health concerns, prolonged hospitalization or, rarely, death

        Local Complications


        Infection can occur with any operation. In the knee, this can be superficial or deep. Infection rates are approximately 1%. If infection occurs, it can be treated with antibiotics but may require further surgery. Very rarely, your new knee prostheses may need to be removed to eradicate infection.

        Blood Clots (Deep Venous Thrombosis)

        These can form in the calf muscles and can travel to the lung (pulmonary embolism). These can occasionally be serious and even life-threatening. If you get calf pain or shortness of breath at any stage, you should notify your doctor.

        Fractures or Breaks in the Bone

        Fractures or breaks in the bone can occur during surgery or afterwards if you fall. To repair these, you may require surgery.

        Stiffness in the Knee

        Ideally, your knee should bend beyond 120 degrees but, on occasion, the knee may not bend as well as expected. Sometimes a manipulation is required. This means going to the operating room where the knee is bent for you under anesthesia.


        The plastic liner eventually wears out over time (usually 15 to 25 years) and may need to be changed.

        Wound Irritation or Breakdown

        The operation will always cut some skin nerves so you will inevitably have some numbness around the wound. This does not affect the function of your joint. You can also get some aching around the scar. Vitamin E cream and massaging can help reduce this.

        Occasionally, you can get reactions to the sutures or a wound breakdown that may require antibiotics or, rarely, further surgery.

        Cosmetic Appearance 

        The knee may look different than it was because it is put into the correct alignment to allow proper function.

        Leg length inequality

        This is also due to the fact that a corrected knee is more straight and is unavoidable.


        An extremely rare condition where the ends of the knee joint lose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).

        Patella Problems

        The patella (knee cap) can dislocate. This means that it moves out of place and it can break or loosen.

        Ligament injuries

        There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or they can tear or stretch out any time afterwards. Surgery may be required to correct this problem.

        Damage to Nerves and Blood Vessels

        Rarely, these can be damaged at the time of surgery. If recognized, they are repaired but a second operation may be required. Nerve damage can cause a loss of feeling or movement below the knee and can be permanent.


        Surgery is not a pleasant prospect for anyone but, for some people with arthritis, it could mean the difference between leading a normal life or putting up with a debilitating condition. Surgery can be regarded as part of your treatment plan. It may help to restore function to your damaged joints as well as relieve pain.

        TKR is one of the most successful operations available today. It is an excellent procedure to improve quality of life, take away pain, and improve function. In general 90-95% of knee replacements survive 15 years, depending on age and activity level.

        Surgery is only offered once non-operative treatment has failed. It is an important decision to make and, ultimately, it is an informed decision between you, your surgeon, your family, and your primary care doctor.

        Although most people are extremely happy with their new knee, complications can occur and you must be aware of these prior to making a decision. Be sure to discuss your concerns thoroughly with your surgeon prior to surgery. If you are undecided, it is best to wait until you are sure this is the procedure for you.

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