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- What are the main factors you should consider
when deciding to have a knee replacement?
First of all, how bad is your pain,
stiffness, swelling?
Secondly, how severe is your osteoarthritis?
Finally, how much is your pain affecting
your quality of life?
Normally, we start with treating
osteoarthritis conservatively.
If you don't respond well to conservative measures,
including physical therapy, cortisone injections,
anti-inflammatory medications,
and sometimes viscosupplementation.
Then we consider an arthroscopy.
That is a vacuum and polishing of the knee.
But if an arthroscopy fails to give you long term relief,
and your pain significantly interferes
with the quality of your life,
then a total knee replacement is considered.
Let's talk about what happens in a knee replacement.
In other words, what's removed,
and what's put in?
In order to understand this,
we have to once again,
start out by looking at the normal parts list.
This time, let's look at the side view of the parts list
of the knee.
Let's look again at the side view
of this hinge joint.
The thigh bone.
The meniscus that sits
on the leg bone.
And the kneecap in the front.
This is the normal knee.
In a severe and advanced arthritic knee,
we have the nice surface
that's usually smooth and Teflon-like
of the thigh bone,
having worn down
chipped off
and also having developed some bone spurs
in the front and in the back.
On the top of the leg bone,
the meniscus has completely worn away.
And also, the back of the leg bone
and often the front of the leg bone,
has developed some spurs.
In a knee replacement,
we are replacing the surfaces
of these bones.
Another way of thinking of this is
when you have a worn out tire,
you have two choices:
You can replace the entire tire,
or you can just get a retread
and replace the surfaces.
In doing a knee replacement,
we just retread the knee.
We replaced just the surfaces.
In fact, we replaced the
surface of the thigh bone
with metal
so that it looks something like this when we're finished.
Cross-hatched
means metal.
And we replace the top of the leg bone
with a layer of very hard plastic
called polyethylene
that is attached to metal.
That inserts on top of the leg bone
often with a peg, such as I've drawn here.
Again, we've replaced the worn out
surfaces of the thigh bone
that is the worn out Teflon,
with metal.
We've replaced the worn out meniscus
with a polyethylene plastic
that attaches to metal,
and we've removed all the bone spurs.
- Each total knee prosthesis is made up of
three basic components.
The femoral, the tibial,
and a plastic spacer that fits between the two.
The femoral and the tibial components
are made up of metal.
Attached to the tibial component is a plastic spacer.
This plastic is thick and very smooth,
which allows the femoral prosthesis to glide
smoothly across its surface.
Most surgeons will also use a patellar component
to replace the surface of the kneecap
where it glides in the femoral groove.
The prostheses are attached to bone with cement.
In order to remove the worn down
degenerate portion of your bone,
the ends of your femur and tibia have to be cut
and removed to make room for the prosthesis.
The tibial component replaces the end of your tibia,
or lower leg bone.
The femoral component replaces the end of your
femur, or thigh bone.
Your menisci, or shock absorbers, are removed,
and the plastic spacer is inserted to take the place
of your meniscus.
An incision is made along the front of your knee
to allow access to the knee joint.
Cutting guides allow us to make meticulous cuts
on the knee so that the components fit precisely,
and the knee returns to its normal alignment.
This is the time your surgeon corrects
any alignment issues such as being
knock-kneed or bowlegged.
No two knees are alike.
(soft rock music)