How would you differentiate between posterior cruciate and anterior cruciate on this MRI? Is the posterior one always the one that appears medially from the back?
Also, are vastus medialis and vastus lateralis always the most posterior muscles on this kinda image?
A) Anterior Cruciate Ligament: attaches anteriorly on the tibia and courses posteriorly to attach on the posterior aspect of the distal femur --> Prevents anterior dislocation
Also, remember that with a when your knee is subject to a strong lateral force, such as in a football injury, the three structures most often damaged are the MCL, ACL, and Lateral meniscus. This is because the tibia internally rotates and therefore the lateral meniscus rubs up against the lateral condyle of the femur and has a tendency to tear.
Actually, apx85 may be correct...here's some more info on this
- The "classic unhappy triad" (O'Donoghue's triad) due to an acute valgus stress on the knee involves the ACL, MCL, and medial meniscus.
- However, recent studies suggest two things:
1. The triad of ACL, MCL and lateral meniscus injury is actually more common than the classic triad following acute valgus stress on the knee
2. In patients that do develop the classic unhappy triad , only the ACL and MCL are acutely injured during the acute valgus stress on the knee, while the injury to the medial meniscus is the result of chronic injury secondary to ACL insufficiency [3]
That is absolutely correct heights. Acutely, Lateral meniscus tear is likely. Chronically, medial meniscus tear is likely.
We are in our MSK block and I talked to a resident and a fellow about this topic and they said that medial meniscus tears occur later because of instability of the knee joint. The resident actually had an ACL tear which he did not get repaired so he said that he is almost inevitably going to get a Medial meniscus tear at some point because of joint instability.
But for the acute injury of athlete's triad, we should be concerned about a lateral meniscus tear. Like you said heights, this is a relatively new finding but could very well be tested on our exam.
Also, on the Netter image that heights posted, notice that the medial meniscus and medical condyle are far away from each other while the lateral meniscus and lateral condyle are rubbing against each other, thus likely to lead to a tear.
It might be confusing because the MCL is connected to the medial meniscus, but somehow this is generally not affected.
The first one's from the side, the second one's from the front...
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