Results, Complications & Indications


Results - Complications - Indications of knee replacement Prothèse Genou





With over twenty years of experience behind us, the results of knee replacement surgery have equaled and perhaps surpassed those of hip replacement surgery. Based on pain, motion and function (ability to walk and climb steps), the results are excellent in 90% of cases. The main indication for surgery is pain relief. In 60% of cases we are able to completely eliminate all pain. In 30% of cases the pain is reduced to an occasional occurrence (e.g. with changes in weather). In 10% of cases patients may continue to have pain requiring pain medication. In addition to pain relief, knee replacement surgery can lead to a significant improvement in knee flexion: an average of 120 degrees of flexion, more with unicompartmental replacements. Patients are usually able to obtain a normal gait, this includes level walking and stair climbing. Usually neither crutches nor canes are required. Swimming, bicycle riding and golf are perfectly feasible following surgery. However, knee replacement surgery is not carried out to allow unlimited athletic activities and we recommend against activities which could lead to wear or loosening of the implant.


The 10% of results judged unsatisfactory can be due to some of the complications we will discuss, or to persistent pain or to insufficient flexion (less than 90°). What are the long term results? Current studies suggest that total knee replacements, as well as partial knee replacement can easily last twenty years. Studies indicate that after ten years 80% to 90% of the implants are still in place. Results tend to gradually deteriorate with time as the implant can work itself loose or wear out. Not all implants last twenty years, but if the original bone cuts were conservative enough, a second implant can be placed without a major technical challenge.


All operations are associated with certain risks. These can be divided into general risks common to all operations( e.g. anesthesia complications) and complications very specific to knee replacement surgery. These can occur at the time of surgery or any time thereafter.


A) Intraoperative Complications: These are quite rare. They can include injury to the artery running directly behind the knee or any injury to the peroneal nerve. Rarely a fracture of the femur or tibia can take place. Also reported are ruptures of the extensor mechanism (patellar or quadriceps tendon).


B) Early Post Operative Complications: Infection is the main concern. This is as serious as it is rare. When an infection does occur, it is important to determine the bacteria responsible for it. Treatment consists of the appropriate antibiotic, as well as another operation to flush out the infection. The implant may or may not need to be removed.

DVT (Deep Venous Thrombosis): Despite the use of a blood thinner, blood clots can form deep in the veins and this complication itself can lead to a more serious complication namely the pulmonary embolus (whereby the clot travels to the lung).

Hematoma: Bleeding into the knee can continue after surgery and require another operation to evacuate the collection of blood.

Knee stiffness can occur after any procedure on the knee, including implant surgery. There are multiple causes for this stiffness, including pain, difficulty obtaining appropriate physical therapy, unusual inflammation, development of a hematoma, etc. A manipulation under anesthesia can be useful in select cases. This is a short procedure which simply involves bending the knee under anesthesia. This breaks up the early adhesions. As a rule this is best done early rather than late (adhesions tend to become more and more dense).

RSD (Reflex Sympathetic Dystrophy): This is quite rare. It is characterized by undue stiffness and pain. Treatment for this can be quite long and frustrating.


C) Long Term Complications:

 These include infection, stiffness and late mechanical complication of the implant.

Late infections are rare. One must remain leery of this complication. An implant can become infected due to a more distant infection (e.g. dental abscess, urinary infection, etc.). Therefore, any hint of infection anywhere in the body needs to be aggressively investigated and treated if present. Late infections usually require major surgery to remove and eventually replace the implant. Rarely a "fusion" needs to be carried out. In this situation, the implant is completely removed and the two bones are fused together.

If there is persistent stiffness long after the knee replacement, a simple manipulation will no longer suffice. At this point the knee may need to be formally opened in order to remove adhesions.

Mechanical complications can be problematic, but can usually be solved by a change of implant.

Instability of the knee can take place at the level of the knee cap or can be due to insufficiency of the collateral ligaments (between the femur and the tibia).

Wear of the implant is associated with any type of implant. It would appear that the use of implants with a rotating plastic component are less prone to this type of problem.

Loosening: This occurs when the implant is no longer rigidly fixed to the underlying bone. This can be a painful condition. It can occur with both cemented and cementless ("bone ingrowth") implants.

Fractures: Trauma at any point can lead to fracture of a bone around the implant. The implant itself may on occasion also break. Breaking of the implant usually is not the result of trauma, but of material fatigue.


Despite the long list of complications that can occur, overall they are quite rare, and by and large, results from knee replacement surgery are excellent.



When is surgery reasonable?

The answer is simple: when the pain continues to be unbearable! The question, of course, is when to move from non-operative to operative treatment. By and large, pain medications control pain but do not change the underlying arthritic problem. The patient himself or herself is the only one who can make the decision to go ahead with surgery. No doctor, friend or relative can truly tell how much pain and discomfort the patient is in. The patient, of course, must be an informed consumer, he or she must be made aware of the potential benefits, as well as the potential complications and limitations of the procedure. There is no such thing as a prophylactic knee replacement operation. One should not be scared into agreeing to surgery for fear that the arthritis will get worse. Even if the arthritis does worsen, the operation will always be possible. Exceptions to this rule would be the gradual development of a major deformity. As long as the patient is healthy, age is not an issue. Therefore, as long as one is healthy, one is never too old to have the operation. One should never undergo knee replacement surgery unless pain is truly disabling. On the other hand, considering the results which can currently be obtained from this type of surgery, it would be a shame not to avail oneself to an operation which can have such a dramatic effect on the quality of life.