So what causes osteoarthritis?
this one's easy.
Despite being the most common,
chronic, degenerative joint disease,
afflicting nearly everybody
over the age of 50,
the etiology of osteoarthritis
remains completely unknown.
We do, however, at least know
some of its risk factors.
Anyone over the age of 65 has osteoarthritis and
oftentimes it can start considerably earlier.
Female gender is a risk factor, any
family history, prior joint trauma
and certainly obesity by virtue of
excess wear and tear on those joints.
In addition, osteoarthritis can be secondary to other disease
processes like diabetes, hemochromatosis, acromegaly
and even gout can cause
osteoarthritic types of manifestations.
So, let's go back to our case for a
moment and look for some key features.
We have an acute-on-chronic picture,
very typical for osteoarthritis.
Worse after activity but morning
stiffness lasting for less than 15 minutes.
Also, typical of osteoarthritis.
The swollen joint can happen as an acute
synovitis on a backdrop of chronic osteoarthritis.
It's not common but it
does certainly happen.
Bony enlargement of the knees due to
these osteophytic growths around the pes
is common especially on radiographs.
and the fact that you have tenderness on the
medial joint line also supports that condition.
So, to recap:
Classic features of osteoarthritis
are those we had in our case.
A chronic disease with periodic flares,
typically precipitated by increased activity.
You're also looking for asymmetric symptoms and with
inexorable progression osteoarthritis of some joints
can literally bring many
people to their knees.
See what I did there?
Now, it has a predilection
for certain joints.
Like the knees, the hips, the lumbar spine
and of course shown here on the left,
the proximal interphalangeal and the distal
interphalangeal joints of the fingers.
Classic physical exam findings as I
alluded to are gonna be bony enlargement,
a limited range of motion, varus deformity
which means being somewhat bowlegged,
crepitus by palpating
the knee while moving it
and of course, joint-line
tenderness as I've mentioned.
So let's take a look at some of the common
radiographic features of osteoarthritis.
The picture on the left here is
a normal radiograph of a knee
and the one on the right is somebody
with severe osteoarthritis.
What you can see right off the bat, the first
distinguishing feature is the joint space narrowing,
particularly in the medial
compartment of the knee.
In addition, you can see
evidence of subchondral sclerosis
which is that hyperlucent
areas just on the tibial plateau.
There's evidence of subchondral
cyst in there as well
and osteophytes basically
broaden the size of the knee
relative to the size of the tibial plateau.