Knee Replacement Surgery
Consult with Us at Great River Orthopaedic Specialists
The upper leg bone (femur) meets the lower leg bone (tibia) to form the
knee joint. The end of the femur consists of two condyles, which are like
runners on each side of the bone. The condyles sit on top of the tibia,
which is like a platform that slightly curves inward. On each side of
the joint, there is an area of contact between the two bones. When the
knee is bent, the condyles of the femur roll and slide on top of the tibia
at these two areas of contact. A third bone, the kneecap (patella), glides
over the front and end of the femur.
In a healthy knee joint, the surfaces of these bones are very smooth and
covered with a tough protective tissue called cartilage. Arthritis causes
damage to one or more of the bone surfaces and cartilage where the bones
rub together. These damaged surfaces eventually become painful and may
cause loss of movement.
There are many ways to treat the pain caused by arthritis. Knee-replacement
surgery usually is considered after other treatment methods have been
tried. In knee-replacement surgery, the bone surfaces and cartilage that
have been damaged by arthritis are removed and replaced with artificial
surfaces made of metal and a very durable plastic material. These artificial
surfaces are called “implants.”
A minimally invasive procedure for knee replacements may help people keep
pace with busy lives. Some patients may benefit from minimally invasive
knee-replacement surgery. The benefits are:
Smaller scar – Only the diseased portion of the knee is removed, leaving a 2-
to 3-inch scar.
Shorter hospital stay – For some people, minimally invasive knee-replacement surgery is
an outpatient procedure. Inpatient stays are shorter than standard total
Faster recovery and rehabilitation time – For many patients, it’s about five weeks.
Greater range of motion – The procedure allow for nearly full range of motion compared to
standard total knee procedures (non-high flex).
As your physician if you are a candidate for this type of procedure.
Minimally Invasive Partial-knee Replacement
If the surfaces on both sides of the bones, as well as the underside of
the patella, are significantly damaged, a total knee replacement usually
is considered. But sometimes there may be significant damage on only one
side of the joint. In these cases, a partial (unicompartmental) knee replacement
may be considered. In a partial knee replacement, only one side of the
joint is resurfaced.
Getting to the Joint
For a partial knee replacement, the patient is taken into the operating
room and given anesthesia. After the anesthesia has taken effect, the
skin around the knee is scrubbed thoroughly clean and then swabbed with
an antiseptic liquid. The knee is flexed about 90 degrees, and the lower
portion of the leg, including the foot, is placed in a special device
to securely hold it in place during the surgery. A tourniquet is usually
applied to the upper portion of the leg to help slow the flow of blood.
An incision is made through the skin, muscle and other soft tissue until
the damaged bone surfaces are exposed. Recent advances in instrumentation
and surgical technique have allowed surgeons to perform some partial knee
replacements through a much smaller incision than those used traditionally.
This less-invasive procedure, which is called MIS™ Minimally Invasive
Solution, is intended to disrupt less of the soft tissue that surrounds
Removing the Damaged Bone Surfaces
Damaged bone surfaces and cartilage are removed. Precision guides are used
to help make sure that the cuts are made at the correct angles so the
bones will align properly after the implants are attached.
Small amounts of the bone surface are removed from the front, end, and
back of the damaged condyle on the femur. This shapes the bone so the
implants will fit properly.
A small portion of the top surface of one side of the tibia is also removed,
making the end of the bone flat.
Attaching the Implants
An implant is attached to each of the bones using a special kind of cement
for bones. The implants are shaped so that the knee joint will move in
a way that is very similar to the way the joint moved when it was healthy.
The implant that fits over the end of the femur is made of metal. Its surface
is rounded and very smooth.
There are two types of implants that fit over the top of the tibia. One
consists of two parts. A metal base plate fits over the part of the bone
that was cut flat. A plastic insert is then attached to the base plate
to serve as the articulating surface between the tray and the metal femoral
implant that covers the end of the femur. The other type of implant consists
of a single piece of plastic that is similar in shape to the metal base
plate and plastic combination. Your physician will decide which implant
is better for you.
Closing the Wound
When all the implants are in place, the surgeon may adjust the ligaments
that surround the knee to achieve the best possible knee function. Then
the surgeon sews the layers of tissue back into their proper position.
A plastic tube may be inserted into the wound to allow fluids to drain
from the site for a few hours after surgery. The edges of the skin are
then sewn together and the knee is wrapped in a sterile bandage. The patient
is then taken to the recovery room.