The vast majority of total knee replacement surgeries are successful; however, complications do occur. About 5% of Medicare patients (ages 65 and older) are re-admitted to the hospital within 30 days for a complication relating to knee replacement surgery.

Below is a list of some potential complications. In rare instances, these complications are life-threatening. A small percentage of patients will require a second, revision surgery.

    Complications involving anesthesia
    Like any major surgery involving general anesthesia, there is a low risk of strokes, heart attacks, pneumonia, and blood clots.

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    Illustration of total knee replacement surgery.

    Blood clots occurring in deep veins, or deep vein thrombosis (DVT), are one of the most common complications of knee replacement surgery. Left untreated, a blood clot can break free from the vein wall, a life-threatening condition known as pulmonary embolism. When caught in time, pulmonary embolism is treatable with anti-clotting medication.

    Of the Medicare patients (65 years and older) who underwent total knee replacement between 2007 and 2010, 0.4% had deep vein thrombosis, 0.3% had pulmonary embolism, 0.3% had a heart attack, and another 0.3% died.

    The knee can become infected. Antibiotics are routinely given at the time of surgery, reducing the risk of infection to less than 1 %. Rarely, the implant is the source of the infection. If the implant is involved in the infection it must be removed and replaced through a second surgery.

    Notably, while the risk of infection decreases as the surgical wounds heal, it never completely goes away. People who receive joint replacements are advised to tell their dentists before any dental procedure. Bacterial infections contracted during dental procedures can affect implants. Antibiotics can be given to prevent this from happening.

    Other risks and complications
    Aside from risks associated with anesthesia and infection, there are other potential complications:

    • A prosthesis component can become loose or dislocate if it does not seal to the bone well or is misaligned.
    • Legs may be slightly different lengths after surgery. In some cases a shoe insert can remedy this problem.
    • The new knee may be stiff. Most people who have undergone knee replacement surgery can bend their knees at least 115 degrees. However, some people develop scar tissue that hinders flexibility. This limited flexibility is more common in people who had limited flexibility before surgery.
    • An allergic reaction to the bone cement can occur. In these cases the bone cement and prosthesis must be removed.
    • Damage can occur to the knee’s patella (knee cap) and/or the soft tissue (muscles, ligaments and tendons) that support the joint between the patella and the femur.
    • In rare cases there is damage to surrounding arteries, veins and/or nerves.

For the most part, complications can be treated. A surgery followed by complications may still be considered successful if pain is alleviated and function improves over the long term.