Factors that influence the stability of a synovial joint include a. shape of articular surfaces, b. presence of strong reinforcing ligaments, c. tone of surrounding muscles, d. all of these.

Video transcript

Hi, everyone. Here's our next question. Which of the following structures of the knee is not included in the unhappy triad. That phrase in quotation marks a, the anterior cruciate ligament AC L B, the medial collateral ligament MC L C, the medial meniscus or D the lateral meniscus. Well, our answer here is choice d the lateral meniscus, this is on the outer side of the knee joint. And so it doesn't tend to get impacted by the same forces that tend to cause an injury called a blown knee. Whereas the other three structures and you see, we have three other answer choices. I'm gonna put an arrow up to unhappy triad. The unhappy triad are the three structures that get impacted more often. And so the AC L MC L and medial meniscus are not our answer because those are the three most often impacted in this type of knee injury. And that usually involves an impact to the knee or the injury that results when the weight bearing foot turns and changes direction while at the same time being firmly planted on the ground. And as you can imagine both these things, both an out outer impact and this sort of direction change with the foot planted are common sports injuries. So both of those events tend to affect our three first choices, which is why they're called the unhappy triad since they're prone to the those injuries. Whereas choice d the lateral meniscus is our answer because it's less likely to be impacted by those sorts of injuries. See you in the next video.