Knee replacement surgery or knee arthroplasty is a major operation, and like any other operation, has its risks and benefits. Serious complications however are rare.

How often do complications occur?

Complications occur in about 1 in 20 cases. These are mostly minor and often resolve by themselves or by available treatment options.

Chronic illness like heart disease or diabetes, smoking and obesity may increase the potential for complications.

What complications can occur?

Complications and risks associated with knee arthroplasty include (1-4):

• Surgical wound infection – The operative wound may be infected in some individuals. Usually a course of antibiotics are prescribed to all patients undergoing knee arthroplasty to prevent such infections.

  Poor wound care and high risk individuals like those with diabetes may lead to infections at the incision site.

  In some the infection may run deeper into the surgical site. In severe cases the prosthetic may need to be replaced due to infection.

  In addition infection from the surgical site may spread all over the body leading to severe sepsis and life threatening complications. This is a rare occurrence.

• Bleeding – Normally all bleeding vessels are secured during the operation using sutures or electric cauterization. Sometimes a bleeder may be left out and this may lead to a later bleeding into the joint.
• Injury to surrounding structures like nerves and tissues that hold up the joint like ligaments and tendons. This can lead to a long term stiffness and difficulty in movement of the joint.
• Foot drop may occur due to damage or stretching of the nerves that control the muscles in the foot. This leads to a weakened and droopy foot. This complication is rare; only occurring in 1in 1000 patients.
• Anesthetic complications – This includes excessive fluctuations of blood pressure and sometimes even death due to anesthetic complications. These are rare.
• Deep vein thrombosis or DVT – This occurs due to blood clots that form in the leg veins as a result of prolonged bed rest and lack of movement during the first few weeks after surgery.

  These clots may break off from their site of origin and get lodged in the brain or in the lungs leading to life threatening complications.

  This can be prevented by early mobilization and wearing special support stockings. Some patients may also need blood thinners or anticoagulant medications to dissolve the clots.

• Injury or fracture of the bone around the artificial joint during or after surgery. Treatment of the condition will depend on the location and extent of the knee replacement surgery.
• Persistent pain and stiffness of the joint. Pain may last the initial few days and subside on taking pain killers. In some patients the pain persists longer.
• Overgrowth of bone around the artificial knee joint. This leads to restricting movement of the knee and joint stiffness. There may be pain around the joint as well. This may require another surgery to remove the overgrowths.
• Excessive scar formation around the wound. This restricts the movement of the knee and may require a surgery to improve movement.
• Dislocation of the knee cap. This also needs further surgery for repair.
• Numbness around the area of the wound. This is usually due to damage to the superficial nerves around the area during surgery.
• Allergy to the bone cement.
• Loosening of the new joint – This may happen due to weakening of the bond between the new joint and the ends of the bone. A replaced knee usually lasts 15 to 20 years with good care and minimal strain. Some people may need revision of the arthroplasty earlier than this.

Further Reading

What is knee arthroplasty? 
When is knee arthroplasty needed?
Recovery from knee arthroplasty
Prevention of knee arthroplasty