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<v ->Now, I grew up in the age of conventional radiography

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and I learned that the distribution of joint disease,

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was critical to accurate diagnosis.

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So I always look at what joints

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and what parts of joints are involved

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and try to differentiate among the various diseases

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of that joint.

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So, if indeed we go ahead and look here,

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I'm showing you the three compartments of the knee.

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On a frontal radiograph,

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the medial femorotibial compartment,

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the lateral femorotibial compartment.

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And on a lateral radiograph, the patellofemoral compartment.

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Now purists will tell me,

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well, we don't stop at three.

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Let's go to four and five.

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The proximal tibiofibular joint,

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communicates with the knee joint normally

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in about 20% of persons.

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And the fabella, cartilaginous or osseous as it may be,

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possesses articular cartilage

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and is part of the knee joint.

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So there are five basic compartments of the knee joint

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but I generally deal with three.

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So here's the summary of the distribution.

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When dealing with osteoarthrosis in men,

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the predominant abnormalities,

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are in the medial femorotibial compartment alone

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or combined with the patellofemoral compartment.

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When dealing with osteoarthrosis in women,

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it more often is the lateral compartment alone

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or the lateral compartment

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combined with a patellofemoral compartment.

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In rheumatoid arthritis,

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there is symmetric medial and lateral disease

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or medial, lateral and patellofemoral compartment.

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And in calcium pyrophosphate disease,

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sometimes it looks like OA but in men particularly.

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Not as helpful in women.

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Isolated patellofemoral involvement,

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should make you think of calcium pyrophosphate disease

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whether or not you see calcification.

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So, here's an example of what is mainly varus osteoarthrosis

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where the medial compartment abnormality dominates.

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This is more common than valgus osteoarthrosis

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where the lateral compartment shows the major findings.

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I want you to look at these images for a moment

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and I'm gonna point out a very interesting finding.

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As you look at patients who have varus OA,

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you will see an increasing malalignment

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between the femur and tibia.

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Now, whether you say it's the tibia moving laterally

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or the femur moving medially, doesn't matter.

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But what happens is, this tubercle now makes contact

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with the inner aspect of the lateral femoral condyle.

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And it can be dramatic

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as shown here also in the sagittal and axial planes.

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So be aware of that.

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Now orthopedic surgeons know about this

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and the general feeling is,

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that if you have extensive medial compartment disease

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and the only abnormality in the lateral compartment

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is right here,

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you can still do a unicompartmental replacement.

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If there's more diffuse involvement

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of the lateral compartment,

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you may have to do a total knee arthroplasty.

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Isolated patellofemoral compartment disease.

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You can see it in osteoarthrosis in women as here.

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It is rare in men.

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And by the way, look at this beautiful example

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of erosion of the distal anterior surface of the femur.

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Now the general thinking might be (indistinct)

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I'm not surprised here's the patella

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rubbing against a femur.

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That's why it's eroded.

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Sounds good to me except this same finding,

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has been reported occurring after patellectomy.

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So that doesn't make a lot of sense

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raising the possibility,

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that in some cases it relates to an effusion

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in the suprapatellar recess, elevated pressure.

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And that's the cause of the eroded femur.

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Just to show you the diseases

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that can produce isolated patellofemoral involvement

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or dominant patellofemoral involvement.

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Calcium pyrophosphate disease.

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Especially in men, I look for this.

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Hyperparathyroidism with subchondral bone resorption,

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favors the patellofemoral compartment

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and a rare disease,

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one of its sight of localization, Wilson's disease,

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with involvement of the patellofemoral compartment.